722 ANATOMY OF VERTEBRATES. 



uterus and lateral canals was the only change perceptible in 

 them.' 1 



As accomplished Naturalists continued to believe and affirm 

 that the young of the Marsupialia quitted the womb and w^ere 

 received into the pouch < in the condition of a gelatinous ovum 

 comparable to a Medusa,' 2 I deemed it requisite to anatomise 

 the rare instance of the uterine foetus of the Kangaroo, in order 

 to demonstrate the conditions of the respiratory, circulating, 

 digestive, and renal systems. ' From the caecum, which was 

 given off from the returning portion of the umbilical loop of the 

 intestine, the large intestine passed backwards to the spine, and 

 was then bent, at a right angle, to go straight down to the anus. 

 The stomach did not present any appearance of the sacculated 

 structure so remarkable in the adult, but had the simple form of 

 a carnivorous stomach. The liver consisted of two large equal 

 and symmetrically disposed lobes. The vena porta? was formed 

 by the union of the vitelline with the mesenteric veins. The 

 diaphragm was perfectly formed. The vena cava inferior was 

 joined, above the diaphragm, by the left superior cava, just at its 

 termination in a large right auricle. The ventricles of the heart 

 were completely joined together, and bore the same proportions 

 to each other as in the adult, — a perfection of structure which is 

 not observed in the embryos of ordinary Mammalia at a corre- 

 sponding period of development. The pulmonary artery and 

 aorta were of nearly the same proportionate size as in the adult : 

 the divisions of the pulmonary artery to the lungs were at least 

 double the size of those observable in the embryo-sheep three 

 inches in length : the ductus arteriosus, on the contrary, was 

 remarkably small. The aorta, prior to forming the descending 

 trunk, dilated into a bulb, from which the carotid and subclavian 

 arteries were given off. The lungs were of equal size with the 

 heart, being about a line in length, and nearly the same in 

 breadth : they were of a spongy texture and of a red colour, like 

 the veins, from the quantity of blood they contained. This pre- 

 cocious development of the thoracic viscera is an evident provision 

 for the early or premature exercise of the lungs as respiratory 

 organs in this animal : and on account of the simple condition of 

 the alimentary canal, the chest at this period exceeds the abdomen 

 in size. The kidneys had the same form and situation as in the 

 adult. The supra-renal glands were half the size of the kidneys. 

 The testes were situated below the kidneys, and were one-half 



1 Erom the Analysis of Rengger's ' Saugethiere von Paraguay' in the Bulletin des 

 Sciences Nat. torn. xxi. p. 469. 



2 cclxiv". p. 342. 



