656 SIR WM. TURNER ON THE PLACENTATION OF HALICORE DUGONG. 



A point of much interest in the study of the placenta in any mammal is the 

 relation between the crypts in which the villi are lodged and the glands of the uterine 

 mucous membrane. On the supposition which w T as at one time entertained that the 

 crypts were the dilated mouths of the uterine glands, there would require to be as many 

 glands as there are villi in order that they may be mutually accommodated. The 

 inadequacy of this hypothesis was, however, pointed out some years ago both by Signor 

 Ekcolani and myself, from the study of the gravid uterus in the Pig and Mare, in 

 which animals we showed that the glands opened on definite areas of the mucous 

 membrane opposite portions of the chorion where there were no villi, and that the 

 uterine crypts were interglandular in position.* Subsequently, in an account of the 

 placentation of the Lemurs, I described a yet more striking example of the inter- 

 glandular position of the crypts, t In the Cetacea again, as illustrated by Orca 

 gladiator,\ I found that though a small proportion of the crypts was associated with 

 glands, the great majority had no such relation, and were interglandular in position. 

 The Dugong also exemplifies the accuracy of this view. If in it all the villi had been 

 lodged in the mouths of glands, then thousands of glands would have been needed for 

 their reception ; whereas, as we have already seen, the glands were sparing in number 

 in the placental area. The only crypts which seemed indeed in the Dugong as if they 

 might be associated with glands were those wider and more deeply situated ones in which 

 the longer villi were lodged. But the shorter crypts, which formed the great majority of 

 the recesses for the villi, were interglandular in the Dugong, and were produced without 

 doubt by an uprising and active growth of the interglandular tissue of the mucous 

 membrane around the villi. The villus and the wall of its crypt were contemporaneous 

 in their growth, and the depth of the crypt corresponded to the length of the villus. 

 The epithelial lining of the crypts is also an important factor in their construction, and 

 its discovery in the Dugong brings its placenta in this particular into harmony with 

 those of the other mammals that I have described. § 



One or two other points of comparison with the specimen described by Dr Harting 

 may now briefly be referred to. In both the allantois was a capacious sac, and 

 extended to opposite pt>les of the chorion, and conveyed blood-vessels in its endo- 

 chorionic layer ; and the arrangement of the larger trunks of the umbilical vessels was 

 also similar in the two specimens. Both also possessed allantoic bodies, which differed 

 somewhat in colour, form, and structure in the younger and more advanced specimens. 

 In Harting's young example they were yellowish- white, round or ovoid, and made up 

 of areolar tissue arranged so as to bound a large number of small cavities, the walls of 

 which were constituted of interlacing elastic fibres united into bundles, and between 



* Lectures on the Comparative Anatomy of the Placenta, Edinburgh, 1876. 



+ Trans. Roy. Soc. Lond., vol. 166, 1876. 



X Trans. Hoy. Soc. Edin., vol. xxvi., 1871. 



§ For a discussion on the physiological relations of the epithelial lining of the crypts, I may refer to the section 

 headed "Physiological Remarks," in my Lectures on the Comparative Anatomy of the Placenta, p. 114, Edinburgh, 

 1876. 



