Paper - The early development of the cat
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Hill JP. and Tribe M. The early development of the cat (Felis domestica). (1924) Quart. J. Microsc. Sci., 68: 513-602.
- 1924 Cat Development: 1. Ovum of the Cat | 2. Process of Cleavage | 3. Formation of the Blastocyst | 4. Discussion | Plates | cat
The early development of the cat (Felis domestica)
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Hill, J. P., and Tribe, M. 1924. The early development of the cat (Felis domestica). Quart. J. Microsc. Sci, 68, 513-602.
Contents
Introduction
Material And Methods
Chapter I.—The Ovum Of The Cat
1. Maturation and Ovulation
2. Structure of the Ovum
3. Fertilization
4. Remarks on Fertilization
Chapter II.—The Process Of Cleavage
1. Description of Cleavage
2. Remarks on Cleavage
3. Yolk-elimination (Deutoplastnolysis) .
Chapter III.—Formation Of The Blastocyst
1. Late Morula and Early Blastocyst Stages from the Uterus
2. Formation of the Didermic Blastocyst
1. Mode of Formation of the Blastocyst
2. History of Embryonal Knot and Covering Trophoblast
3. Prochordal Plate
List Of References
Introduction
Our knowledge of the early development of the Cat, as indeed of the Carnivora in general, is singularly incomplete. Th. L. W. Bischoff, in his classical monograph ' Entwicklungs- geschichte des Hunde-Eies ' published in 1845, provided the first account of the development of a Carnivore from the unsegmented egg onwards and, considering the date of his work, his achievement was really a remarkable one. In addition to later embryonic stages, he described and figured a series of segmenting ova and blastocysts of the Dog, with such fidelity and accuracy that his account is, even today, of the greatest interest and value. He recognized and figured the germinal vesicle of the full-grown ovarian ovum and the refractive granules (' Dotter ') present in the cytoplasm of the latter. He observed the persistence of part of the discus proligerus round the unsegmented tubal egg, and noted its thick zona and the numerous sperm-heads imbedded in it. He figured the two-celled egg with what are evidently two polar bodies situated in the plane of cleavage. He described and figured the three-celled and four-celled stages, his figures of the latter showing quite accurately the characteristic cross- shaped arrangement of the blastomeres. He figured three later tubal eggs, said to be composed of eight, ten, and eighteen blastomeres respectively, and he also illustrated and described a series of morulae and blastocysts from the uterus. He recognized the delicate membranous wall of the blastocyst lying inside the zona and also ' den runden und gleichmassig dunkeln Fruchthof ', and since he found that the latter is situated in the former, he termed this vesicular stage ' die Keimblase '.
No further contribution to our knowledge of early Carnivore development appears to have been made until 1876. In that year E. A. Schafer (now Sir E. Sharpey Schafer) gave an account (45) of the structure of blastocysts of the Cat, possessing a bilaminar embryonal area, one-sixtieth of an inch (0-4 mm.) in diameter. In 1897 Bonnet (14), in his paper on the development of the Dog, described and figured (his figs. 1-3, Taf. 80-1) three eggs of the Cat, one unfertilized, a second with two pronuclei, and a third divided into nine blastomeres of unequal size. He obtained no early material of the Dog, and begins his description of the development with blastocysts 1-5x1-2 mm. in diameter.
In 1911 there appeared a valuable paper by R. van der Stricht (55) entitled ' Vitellogenese dans l'ovule de chatte '. This paper, as is indicated by the title, is primarily concerned with providing a detailed account of the growth of the ovarian ovum, including the process of vitellogenesis in the Cat, but it also includes most valuable chapters dealing with matura- tion, fertilization, and the early stages of cleavage, though the cleavage process is not followed in detail beyond the three- celled stage. It also contains important data relating to breeding habits, oestrus, and ovulation.
In the same year there appeared yet another paper, that of W. H. Longley (37), likewise dealing with the phenomena of maturation and ovulation, the structure of the ovum and the first cleavage division in the Cat.
The most recent contribution to our knowledge of Carnivore development we owe to 0. van der Stricht. In two papers (53, 54), published in 1923, he has described the structure of a series of blastocysts of the Dog ranging from 0-20 to 1-5 mm. in diameter, and has traced the history of the inner cell-mass. His observations, which are referred to later, whilst agreeing in most respects with our own, show that there are certain very interesting differences in the details of the differentiation of the inner cell-mass in the two forms. We are greatly indebted to Professor van der Stricht for affording us the opportunity of examining his preparations of these blastocysts and also of earlier rnorula stages which he has not yet described.
We desire to express our thanks to Mr. F. J. Pittock for invaluable help in the preparation of the material, the micro- photographs and models, to Mr. T. L. Poulton for the drawings of the models represented in Text-figs. 1-8, to Miss M. Rhodes for figs. 5-9 (PI. 25), and to Mr. W. Pilgrim for figs. 1-4 (PI. 24). To the Government Grant Committee of the Boyal Society we are indebted for grants in aid of our work.
Material and Methods
The material which forms the basis of this paper has all been obtained from cats of unknown origin, which came into our hands shortly after death. Its collection was begun in 1909, with the object primarily of obtaining demonstration material for teaching purposes, and has involved the examination of some hundreds of females, only a small proportion of which yielded early stages. We have rejected for the purposes of this paper all eggs which appeared abnormal or whose state of preservation was unsatisfactory. The material that remains forms a fairly graded series extending from the fertilized egg through early and late cleavage stages up to the completed blastocyst in which the definitive embryonal area is established. Although our material, more especially of the early cleavage stages, is not abundant enough to enable us to settle con- clusively certain problems, e. g. the significance of the ' corps enigmatique ', and the very interesting question of the lineage of the central cells which furnish the embryonal knot of the early blastocyst, it is nevertheless sufficiently complete to enable us to give what we hope is a fairly adequate account of the cleavage process and the formation of the blastocyst and its constituent layers in Felis, and thus to provide for the first time a connected account based on modern methods of the early ontogeny of a Carnivore.
Owing to the convoluted character of the Fallopian tubes, their small diameter and relatively thick walls, the Cat is not altogether an ideal subject from which to obtain cleavage stages. In cases where the condition of the corpora lutea and the absence of uterine swellings indicated the presence of eggs in the tubes, our normal procedure was to dissect away the folds of the peritoneum supporting the tube so as to enable the latter to be straightened out. It was then cut through, close to its entrance to the uterus, and perfused with the fixing fluid by means of a pipette provided with a strong rubber bulb. In this way the ova were washed out into a crystal dish, and were afterwards searched for under the higher powers of a Zeiss—Greenough binocular microscope. We have also employed the method advocated by R. van der Stricht and other workers (cf. Longley, p. 143) of expressing the contents of the straightened-out tube on to a slide, by firmly stroking the tube (preferably cut into two or more segments) along its length with the back of a scalpel. We regard this as a very useful method.
As fixatives we have employed the fluids of Plemming and Hermann as well as picro-nitro-osmic acid, with satisfactory results. In order to prevent loss during imbedding, we fastened each egg to a thin slice of brain-cortex by means of a thin solution of photoxylin (0.5 to 1 per cent.). Sections were cut by the Minot rotary microtome, mostly at 6 µm, and were stained with Heidenhain's iron haematoxylin.
We have prepared wax-plate models of a number of cleavage stages, which are illustrated in Text-figs. 1-8. These have proved invaluable more especially in tracing out the lineage of the central cells of the morula from which the embryonal knot is derived, and in demonstrating the occurrence of a process of overgrowth or epiboly, whereby the central cells come to be completely enclosed by the future trophoblastie cells.
Migration of Eggs
In view of recent observations (cf. Corner, 19) on the migration of ova from one uterus into the other in the Pig, we take this opportunity of recording a case in a cat which came under our notice in collecting the material described in this paper. In this particular cat (9.9.5.12) one ovary showed no visible corpora lutea, but the related uterus possessed two uterine swellings, one low down at the junction of the uterus Avith the vagina and the other higher up. The former swelling contained an abnormal embryo, the latter a normal one. The other ovary showed three or four corpora lutea, and the uterus a single uterine swelling. We think this case affords strong presumptive evidence of migration.
Duplication of Uterine Lumen
We also venture to record here an interesting case of duplication of the uterine lumen. In Cat 27.1.10 one of the uteri possessed two lumina, which commenced close to its upper extremity and con- tinued through its entire length quite separate and distinct and at its lower end opened by separate openings into the
Sixteen-celled Eggs
Three eggs of this stage are available for description, all obtained from one cat (8.9.5.12). They are of very great interest inasmuch as the two constituent parts of the future blastocyst are now clearly distinguishable. The future inner cell-mass or embryonal knot is represented by two centrally placed cells, the future trophoblast by fourteen peripheral blastomeres which enclose the central cells either partially or completely.
Egg 20 (8 C). Diameter inside zona, 009 x 0-069 x 0-07S mm. Zona thin, 00024 mm.
Four views of the model of this egg are shown in Text-fig. 6 a, b, c, d, and a combined view of two sections in fig. 21, PL 27. The egg, now in the stage of a morula, consists of fourteen peripheral or trophoblastic cells and two centrally placed cells which are all but completely enclosed by the former. The peripheral blastomeres are spherical and are in contact only over small contiguous areas of their surfaces. They contain fat-globules in fair abundance (fig. 21, PI. 27) and are similar though they differ somewhat in size, e. g. blastomere 2 measures 0028 x 0-024 x 0-018 mm. in diameter, blastomere 13, 0-028 x 0026x0026 mm.
Text-fig. 6. Four views, a, b, c, d (section), of model of egg 20, sixteen-eelled stage. Blastomeres 5 & 12 are the central cells, x about 300.
The two central blastomeres (Text-fig. 6 d, 12 & 5), in spite of their very different destiny, do not appear to differ from the peripheral in any recognizable respect except position. They are here nearly completely enclosed, but it is an interesting and significant fact that the outer end of central blastomere 12 is visible in the model (Text-fig. 6 c) through the gap at one pole of the mornla, bounded by blastomeres 13, 15, 14, and 16. Text-fig. 6 d, representing the cut surface of a vertical section of the model, illustrates this relation as well as the position of the central blastomeres (5 & 12), and affords conclusive evidence in favour of the occurrence of epiboly, i. e. of a process of over- growth whereby the central cells become secondarily enclosed by the peripheral.
The two central cells differ slightly in size, blastomere 12 measuring 0-024x0-031 xO-24 mm., and 5, 0-018 x 0-028 x 0-024 mm. They are thus of very much the same average size as the peripheral cells. As concerns their origin we think their relations to each other and to the peripheral cells indicate pretty definitely that they have arisen by the slightly unequal division of a single parent cell which we suggest is the large blastomere of the seven-celled stage, representing an undivided blastomere of the four-celled stage.
[1X2]+[4]+[3+(1X2)]+[3+(1X2)]=2C +14
If our suggestion is accepted then the constitution of the morula might be represented as follows :
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- 1924 Cat Development: 1. Ovum of the Cat | 2. Process of Cleavage | 3. Formation of the Blastocyst | 4. Discussion | Plates | cat
Reference
Hill, J. P., and Tribe, M. 1924. The early development of the cat (Felis domestica). Quart. J. Microsc. Sci, 68, 513-602.
Cite this page: Hill, M.A. (2024, June 26) Embryology Paper - The early development of the cat. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Paper_-_The_early_development_of_the_cat
- © Dr Mark Hill 2024, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G
