1880.] VARIATION IN EQUUS ASINUS. 7 



Canines long or short, sexual variation. 



Premolars: small "Wolves' teeth" occasionally present in front 

 of four anterior molars. 



Stomach often presents a very marked central transverse constric- 

 tion where cuticular mucous joins the villous. 



Ccecum sometimes retains the form it presents in eight months' 

 foetus ; its apex sometimes very elongated and pointed. 



Colon. — Longitudinal muscular bands vary in size and in number 

 at different parts of the bowel. 



Liver. — Lobes vary in form and much in size. Ligaments differ 

 in degree of development, especially falciform ligament, which some- 

 times runs as far backwards as umbilicus, containing a pervious vein 

 in its thiu free margin. 



Parovarium. — On outer surface of broad uterine ligament, some- 

 times large, often obsolete. 



Male mamma often extremely large. 



Thyroid body varies much in form, especially in the size of the 

 band connecting its lateral masses. Gonchial cartilages prolonged 

 downwards by small rounded band to lateral part of guttural pouch 

 and to posterior angle of stylohyal. A remarkable peritoneal band 

 sometimes runs from the csecum to the omentum major, reminding 

 us of a condition we have noted in one form of Macacus, 



Angiology. 



Anterior aorta often entirely absent. Sometimes a large anterior 

 mediastinal branch passes downwards from this vessel. The dorsal 

 and posterior cervical vary in their relations to each other. Generally 

 these vessels are united on the right side and distinct on the left ; 

 but this condition may be reversed. The cervical may become united 

 by a well developed subcostal with the sixth costal as giveu off from 

 the posterior aorta ; but this is not constant. The vertebral passes 

 through or below the seventh cervical transverse process. The 

 submaxillary may arise directly from the carotid instead of from the 

 external carotid. External pectoral arises from internal pectoial, or 

 axillary. 



Posterior aorta. — Bronchial and oesophageal often arise by common 

 root, or are distinct. Renal may supply suprarenal capsules and 

 kidney; or the former may be supplied directly by a branch from the 

 posterior aorta. Spermatics — one sometimes considerably more an- 

 teriorly placed than the other, even given off by posterior mesenteric. 

 Between internal iliacs occasionally a small middle sacral arises. The 

 obturator^ epigastric, and inguinal sometimes arise from external iliac. 

 The origins of the profunda and of the artery of the cord often 

 vary. 



The medullary artery of the femur is sometimes given off through 

 the foramen at the anterior part of the bone instead of at the inter- 

 nal surface of the bone. The artery of the humerus is similarl)"^ 

 variable. The circumflex of the toe is variously formed in different 

 cases. 



Thus from these examples we see the arteries are the most fre- 



