Book - Vertebrate Zoology (1928) 35
Vertebrate Zoology G. R. De Beer (1928)
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Chapter XXXV Blood Relationships Among The Chordates
The various species of animals differ not only in their structure, their method of development and their habits, but also in the chemical composition of their tissues. The most useful tissue to take in this connexion is the blood. Now, chemical methods are not sufficiently refined to detect the difference between the bloods of two animals and to estimate the degree of similarity which they show. It is possible, however, to have recourse to biological methods by making use of the property which animals possess of developing immunity. If horse 's blood , for example , is injected into the vascular system of a rabbit, the rabbit will after a time produce a substance in its blood which reacts to horse's blood, and precipitates it. This is the same principle as that used for preparing antitoxins for certain diseases. As to how the antitoxin or antiserum is produced, little is known, but it suffices for present purposes to realise that in the hypothetical case just described, rabbit's blood immunised against horse's blood will always precipitate horse's blood, to the extent of ioo per cent. This means that anti-horse serum, as it may be called, is specific against horse, and it is a matter of no importance what kind of animal has been used to produce the antiserum. But the specificity against horse is not quite complete. Anti-horse serum, as it may be called, will produce no effect whatever if mixed with, say, blood of a bird ; but it will produce a slight precipitation with blood of pig, and still more with blood of ass. This means that the blood of horse is more similar to that of ass than to that of pig, as regards its chemical composition, and this is just what would be expected from a knowledge of the comparative anatomy and embryology, and from the palaeontology regarding these three species.
The precipitin blood-tests therefore furnish a means for estimating the relative similarities between the bloods of different animals, and they are not only a biochemical proof of the theory of evolution, but also an index for classification.
The following are a few tables showing the relative affinities between the bloods of a number of vertebrates : *
Anti-human serum, mixed with blood of : —
Man
gives
100 per
cent.
precipitation
Gorilla
>y
64
>
»>
Orang Outang
n
42
>
- »
Baboon
t>
29
>
»
Ox
>>
10
1
tt
Sheep
it
10
>
>i
Deer
>>
7
7
jj
Horse
„
2
,
>>
Marsupial
»»
,
»
These results show several interesting points. In the first place, the great similarity between the blood of man and that of the gorilla should dispel any doubt (should any be left) concerning the evolution of man from lower mammals. The precipitation percentages show that human blood is more like that of the apes than that of the baboon, and more like the latter than the blood of animals like horse and deer. This fits in perfectly with evidence derived from other sources. It is also interesting to note that two animals which are believed to be closely related to one another like ox and sheep, should show the same degree of dissimilarity to man. The relationship between sheep and ox can also be tested by immunising a rabbit to sheep blood .
Anti-sheep serum mixed with blood of : —
Sheep gives 100 per cent, precipitation.
Ox „ 75
Antelope ,, 67 „ ,,
Reindeer ,, 35 „ „
The relationship between sheep and ox is here definitely shown to be close.
- FromNuttall.
Some of the most interesting results are those which refer to the relative affinities between the various groups of reptiles, and between them and the birds.
Anti-fowl egg serum mixed with blood of : —
Crocodile, gave a positive result (precipitation) in 50 per cent, of cases. Chelonian ,, ,, ,, ,, 40 ,, ,, Lacertilian ., ,, ,, ,, 7 ,, ,, Ophidian ,, „ ,, ,, 6 ,, ,,
These results show that the reptiles (alive now) nearest akin to the birds are the crocodiles, which again corroborates all the evidence from other sources. It further indicates that the crocodiles and turtles are more closely akin to one another than they are to the lizards and snakes, which, again, are fairly closely allied to one another. This is further shown by the following : —
Anti-chelonian serum mixed with blood of : —
Chelonian gave a positive result in 87 per cent, of cases. Crocodile „ „ „ 25 Lacertilian ,, ,, ,, o „ ,, Ophidian „ ,, ,, 6 „ ,,
Besides the precipitin tests, there are other methods of estimating the blood-relationships of vertebrates. For one thing, it is found that blood of any particular species has the power of destroying the blood-corpuscles of other species, to an extent varying with the remoteness of the relationship between them. Again, it is found that the degree of virulence with which an animal will suffer from a human disease varies with its degree of kinship to man. So syphilis attacks the chimpanzee more seriously than the orang, and the latter more than the baboon. Lastly, attention may be called to the so-called blood-groups, into which the human race is divided. There are four of these blood-groups, and they are due to two agglutinating substances, which may be absent, or one, or the other, or both may be present, in the blood of a man, and cause clotting when the blood is mixed with that of another incompatible group. Incidentally these groups are further interesting in that there is reason to believe that they are inherited by means of Mendelian factors, but their main interest from the present point of view lies in the fact that the blood-groups and agglutinating substances are also found in monkeys. Here, therefore, are definite biochemical characters which are shared by monkeys and man, and which were derived from a common ancestor.
Literature
Landsteiner, K., and Miller, C. P. Serological Studies on the Blood of the Primates. Journal of Experimental Medicine, vol. 42, 1925.
Nuttall, G. H. F. Blood Immunity and Blood Relationship. Cambridge University Press, 1904.
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- Vertebrate Zoology 1928: PART I 1. The Vertebrate Type as contrasted with the Invertebrate | 2. Amphioxus, a primitive Chordate | 3. Petromyzon, a Chordate with a skull, heart, and kidney | 4. Scyllium, a Chordate with jaws, stomach, and fins | 5. Gadus, a Chordate with bone | 6. Ceratodus, a Chordate with a lung | 7. Triton, a Chordate with 5-toed limbs | 8. Lacerta, a Chordate living entirely on land | 9. Columba, a Chordate with wings | 10. Lepus, a warm-blooded, viviparous Chordate PART II 11. The development of Amphioxus | 12. The development of Rana (the Frog) | 13. The development of Gallus (the Chick) | 14. The development of Lepus (the Rabbit) PART III 15. The Blastopore | 16. The Embryonic Membranes | 17. The Skin and its derivatives | 18. The Teeth | 19. The Coelom and Mesoderm | 20. The Skull | 21. The Vertebral Column, Ribs, and Sternum | 22. Fins and Limbs | 23. The Tail | 24. The Vascular System | 25. The Respiratory system | 26. The Alimentary system | 27. The Excretory and Reproductive systems | 28. The Head and Neck | 29. The functional divisions of the Nervous system | 30. The Brain and comparative Behaviour | 31. The Autonomic Nervous system | 32. The Sense-organs | 33. The Ductless glands | 34. Regulatory mechanisms | 35. Blood-relationships among the Chordates PART IV 36. The bearing of Physical and Climatic factors on Chordates | 37. The origin of Chordates, and their radiation as aquatic animals | 38. The evolution of the Amphibia : the first land-Chordates | 39. The evolution of the Reptiles | 40. The evolution of the Birds | 41. The evolution of the Mammalia | 42. The evolution of the Primates and Man | 43. Conclusions | Figures | Historic Embryology
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