Z8600021 at 22:45, 27 Ocak 2013

2013-01-27T22:45:23Z

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	==~~Plate 5~~. ~~Photographs showing changes occurring in the auricle of the human fetus during the fourth month~~==		==Fig. 50. Embryo No. 2274, 113 mm CRL==

	~~The photographs shown on plate 5 represent~~ the ~~changes occurring~~ in the ~~auricle during the fourth month~~ of ~~intrauterine life. As compared with~~ the ~~photographs on plate 4~~, the ~~principal change is a relative decrease~~ in ~~the size~~ of the ~~crus helicis and tragus~~. ~~Corresponding to~~ this, it ~~is possible~~ to ~~recognize~~ a ~~conchal cavity which has heretofore been nothing more than a cleft~~. ~~The concha~~ in the ~~first two photographs~~ (~~figures 42~~ and 43) ~~appears to me a little exaggerated~~, ~~due~~, ~~probably~~, to the ~~shrinkage of the auricle~~. ~~Judging from the preceding and succeeding photographs~~, ~~the average auricle at this time would be somewhat plumper~~ in ~~appearance~~. ~~Owing to the fact that these~~ are ~~thinner~~, ~~one can see for the first time the presence of~~ the plica principalis.		Figure 49 shows a marked development of the transverse folds in the region of the anthelix, which were first described by Schwalbe and interpreted by him as temporary representatives of the longitudinal folds seen in some of the long-eared mammals. The fact that they are so irregular in occurrence, however, as can be seen by this and the next plate, makes it doubtful whether these folds can be safely interpreted as phylogenetic rudiments. I am inclined rather to attribute them to a redundancy of the soft tissues of the anthelix. This specimen illustrates very well the difference in character between the auricular derivatives of the mandibular bar (cms helicis and tragus) and the derivatives of the hyoid bar (scapha-helix, anthelix, antitragus, and lobule). In the last specimen on this plate ([[:File:Streeter1922-fig50.jpg\|fig. 50]]), in contrast with [[:File:Streeter1922-fig49.jpg\|figure 49]], there are no distinct transverse folds, but the plica principalis is more prominent.


	~~In some cases~~ the ~~right ear was selected~~ and ~~reversed for convenience~~ in ~~comparison~~. ~~These are indicated by~~ the ~~letter R~~. ~~All~~ the photographs are ~~taken at an enlargement~~ of ~~6 diameters~~.
			Plate 5. Photographs showing changes occurring in the auricle of the human fetus during the fourth month

			The photographs shown on plate 5 represent the changes occurring in the auricle during the fourth month of intrauterine life. As compared with the photographs on [[:File:Streeter1922-plate04.jpg\|plate 4]], the principal change is a relative decrease in the size of the crus helicis and tragus. Corresponding to this, it is possible to recognize a conchal cavity which has heretofore been nothing more than a cleft. The concha in the first two photographs (figures [[:File:Streeter1922-fig42.jpg\|42]] and [[:File:Streeter1922-fig43.jpg\|43]]) appears to me a little exaggerated, due, probably, to the shrinkage of the auricle. Judging from the preceding and succeeding photographs, the average auricle at this time would be somewhat plumper in appearance. Owing to the fact that these are thinner, one can see for the first time the presence of the plica principalis.

Z8600021: ==Plate 5. Photographs showing changes occurring in the auricle of the human fetus during the fourth month== The photographs shown on plate 5 represent the changes occurring in the auricle during the fourth month of intrauterine life. As compared with th

2013-01-27T22:08:20Z

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==Plate 5. Photographs showing changes occurring in the auricle of the human fetus during the fourth month==

The photographs shown on plate 5 represent the changes occurring in the auricle during the fourth month of intrauterine life. As compared with the photographs on plate 4, the principal change is a relative decrease in the size of the crus helicis and tragus. Corresponding to this, it is possible to recognize a conchal cavity which has heretofore been nothing more than a cleft. The concha in the first two photographs (figures 42 and 43) appears to me a little exaggerated, due, probably, to the shrinkage of the auricle. Judging from the preceding and succeeding photographs, the average auricle at this time would be somewhat plumper in appearance. Owing to the fact that these are thinner, one can see for the first time the presence of the plica principalis.

In some cases the right ear was selected and reversed for convenience in comparison. These are indicated by the letter R. All the photographs are taken at an enlargement of 6 diameters.

Specimens are from the Carnegie Collection, and length given is crown-rump.

<gallery>
File:Streeter1922-fig42.jpg|Fig. 42. Embryo No. 1724, 66.2 mm.
File:Streeter1922-fig43.jpg|Fig. 43. Embryo No. 2328, 65 mm.
File:Streeter1922-fig44.jpg|Fig. 44. Embryo No. 2118, 69 mm.
File:Streeter1922-fig45.jpg|Fig. 45. Embryo No. 981, 85 mm.
File:Streeter1922-fig46.jpg|Fig. 46. Embryo No. 1845, 87 mm.
File:Streeter1922-fig47.jpg|Fig. 47. Embryo No. 1449, 87.3 mm. (R.)
File:Streeter1922-fig48.jpg|Fig. 48. Embryo No. 2003, 103.5 mm.
File:Streeter1922-fig49.jpg|Fig. 49. Embryo No. 1858, 100 mm. (R.)
File:Streeter1922-fig50.jpg|Fig. 50. Embryo No. 2274, 113 mm. (R.)
</gallery>

{{Streeter1922}}

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[[Category:Human]] [[Category:Hearing]] [[Category:Second Trimester]]

File:Streeter1922-fig50.jpg - Revision history

Z8600021 at 22:45, 27 Ocak 2013

Z8600021: ==Plate 5. Photographs showing changes occurring in the auricle of the human fetus during the fourth month== The photographs shown on plate 5 represent the changes occurring in the auricle during the fourth month of intrauterine life. As compared with th