COMPARATIVE ANATOMY. 



there is an obscure division into two 

 blind sacs, (as in the gibbon, or long- 

 armed ape :) this distinction is more 

 strongly expressed in the lori, (lemur 

 tardigradus,) so as to form a manifest ap- 

 proach to the uterus bicornis. 



2. A simple uterus with straight or 

 convoluted horns (uterus bicornis.) 

 They are straight in the bitch, in the bats 

 of this country, in the sea-otter, seal, 

 &c. ; somewhat convoluted in the ceta- 

 cea, mare, and hedge -hog, and still more 

 tortuous in the bisulca. 



3. A double uterus, having the appear- 

 ance of two horns, which open separately 

 into the vagina ; this is seen in the hare 

 and rabbit, (uterus duplex.) 



4. A double uterus, with extraordinary 

 lateral convolutions, is met with in the 

 opossum and kanguroo, (uterus anfrac- 

 tuosus. 



These various forms undergo different 

 changes in the pregnant state. 



The alteration in the simple uterus is, 

 on the whole, analogous to that which 

 occurs in the human female. 



The pregnant uterus bicornis suffers a 

 different change in those animals which 

 bear only one at a time, from that which 

 it undergoes in the multipara. The foetus 

 of the mare is confined in its situation to 

 the proper uterus. In the cow it extends 

 at the same time into one of the horns, 

 which is enlarged for its reception. In 

 those, on the contrary, which bring forth 

 many young at once, as also in the 

 double uterus of the hare and rabbit, 

 both cornua are divided by contracted 

 portions into a number of pouches cor- 

 responding to that of the young ; and 

 where those horns are straight in the un- 

 impregnated state, as in the bitch, they 

 become convoluted. 



The uterus of the opossum and kangu- 

 roo suffers the least change from its usual 

 appearance in the impregnated state. 

 For these strange animals bring their 

 young into the world so disproportion- 

 ately small, that they appear like early 

 abortions. 



The passage of the foetus, in the opos- 

 sum tribe and the kanguroo, from the 

 cavity of the uterus into the false belly, 

 where it adheres by its mouth to the nip- 

 ple, presents one of the most singular and 

 interesting phenomena in the whole cir- 

 cle of comparative anatomy. Physiolo- 

 gists have not yet ascertained, whether 

 the embryo possesses, at any period, a 

 connection with the uterus similar to 

 that which is observed in the other mam- 

 malia : but it appears very probable, that 

 tfce processes, which follow the passage 



of the ovum from the ovarium,are entire- 

 ly different in these animals, from those 

 which take place in the other mammalia. 

 Neither has the precise period, at which 

 the foetus enters the false belly, been 

 hitherto shewn, 



The following statement of the sub- 

 ject, as far as it is at present known, is 

 derived from Mr. Home's paper. (Phil. 

 Trans. 1795.) 



The uterus and lateral canals, in their 

 pregnant state, are distended with a very 

 adhesive jelly of a bluish white colour ; 

 which also fills the oval enlargements of 

 the Fallopian tubes. 



" In the cavity of the uterus," says Mr. 

 Home, " I detected a substance which 

 appeared organized ; it was enveloped in 

 the gelatinous matter, and so small as to 

 make it difficult to form a judgment re- 

 specting it; but when compared with the 

 foetus after it becomes attached to the 

 nipple, it so exactly resembled the back- 

 bone with the posterior part of the skull, 

 that it is readily recognized to be the 

 same parts in an earlier stage of their for- 

 mation." 



This substance has been represented 

 in a plate ; but the engraving does not, 

 in our opinion, possess the slightest 

 similitude to the parts mentioned by Mr. 

 Home. 



The size of the foetus at the time it 

 leaves the uterus is not yet ascertained. 

 The smallest, which has been hitherto 

 found in the false belly, weighed twenty- 

 one grains, and was less than an inch in 

 length. In another instance it was " thir- 

 ty-one grains in weight from a mother of 

 fifty-six pounds. In this instance the 

 nipple was so short a way in the mouth^ 

 that it readily dropped out ; we must 

 therefore conclude that it had been very 

 recently attached to it. 



" The foetus at this period had no navel 

 string, nor any remains of there ever 

 having been one ; it could not be said to 

 be perfectly formed, but those parts 

 which fit it to lay hold of the nipple 

 were more so than the rest of the body. 

 The mouth was a round hole, just 

 enough to receive the point of the nip- 

 ple ; the two fore-paws, when compared 

 to the rest of the body, were large and 

 strong, the little claws extremely distinct; 

 while the hind-legs, which are afterwards 

 to be so very large, were both shorter and 

 smaller than the fore or.es." 



" The mode in which the young kan- 

 guroo passes from the uterus into the 

 false belly has been matter of much spe- 

 culation ; and it has even been supposed 

 was an internal communica- 



