4- 



MORPHOLOGY OF THE 



In the former it lies behind the various coils of jejunum and 

 ileum, while in the latter it hes in front of them. 



The absence of all adhesions, and the short ascending 

 colon, suggest at once an embryonic type of abdominal cavity. 



Method of Investigation. 



This investigation was made by means of microscopic 

 sections, and l)y the dissection of seventy-four embryos, as 



well as by the dissection 

 of numerous adult cats. 

 Several of these embryos 

 were very kindly sent 

 me by Profs. Wilder and 

 Gage, of Cornell Univer- 

 sity. The study of de- 

 velopment by means of 

 dissection is a somewhat 

 antique and abandoned 

 method, and yet it was 

 found to be of the great- 

 est possible service in this 

 investigation. If an em- 

 bryo of only 12 mm. be 

 treated by the progres- 

 sive alcohol method, the 

 abdominal organs will be 

 sufficiently hardened so 

 that they may be indi- 

 vidually removed, and 

 yet they will retain their 

 normal shape; or the 

 body wall of the embryo 

 may be entirely taken 

 away and the viscera al- 

 lowed to remain in situ. Treated in this manner, the viscera 

 retain perfectly their relations to each other, and can be 



Fig. I. 



Thf^ l)ody wall of an embryo 34 mm. has 

 been removed. The viscera are seen in situ. 

 (Enhirged 5.3 diameters.) r. v.^ light ven- 

 tricle. /. r/., left aviricle. I. v., left ventricle. 

 ^, liver. intestines. aZ., allantois. lu. 

 \\\ng. s., stomach, sp., spleen. W. 6., 

 Wollllan body. o. omentum. 



