666 messhs. b. c. a. wixdli: and p, g. parsons ox [Dec. 17- 



the Museum of the College of Surgeons (42) there is a feeble 

 though distinct bilauiination exactly corresponding with that of the 

 maaseter. The external pterygoid rises from the alispheuoid above 

 and in front of the origin of the internal, it has only one head and 

 is always the smaller of the two muscles. The fibres run hori- 

 zontally backward and outward, and are inserted into the inner 

 side of the neck of the condyle. The internal maxillary artery 

 runs below the muscle in the groove between it and the internal 

 pterygoid, indeed in our specimen of Duiker-bok (49) the artery 

 lay between the two muscles. 



The nerve-supply of all the preceding muscles has been carefully 

 looked for and in most cases found in all the animals which we have 

 dissected. In every case it was as in Man. 



Depressor mandibuli (Digastric). — As a rule this muscle rises from 

 the paroccipital process on its anterior border, iu some cases it also 

 comes from the paramastoid process, though in the literature of 

 the subject these two processes are often confounded with one 

 another. The central tendon and anterior attachments vary, as will 

 be seen from the following details. 



In the Hippopotamida 3 . Humphry (2) says that the anterior 

 belly is connected with the hyomental muscle, while in Cuvier and 

 Laurillard's plate (3) there is apparently only an anterior belly, the 

 muscle rising by tendon from the paroccipital process and being 

 inserted into the middle of the body of the jaw. 



In the Suidae, Lesbres (4) says that there is only one belly which 

 rises from the paroccipital, and this agrees with Vrolik's de- 

 scription of the Babirusa (VIII.). 



In our Eed-Eiver Hog (11) we found that the posterior belly 

 was absent and that no nerve was supplied to it by the facial. In 

 Cuvier and Laurillard's Pig (7), however, two distinct bellies are 

 figured. 



In the Peccary (13, 14) two bellies and a distinct central tendon 

 are found, and the nerves from the facial and mylo-hyoid are both 

 present (14). 



In the Camel (19) we are indebted to the kindness of Dr. Peter 

 Thompson, who has placed some unpublished notes and drawings 

 at our disposal. In his specimen two bellies with the usual nerve- 

 Bupply were found, the posterior rising from the paroccipital, the 

 anterior, much larger, being inserted by a thin flattened tendon near 

 the insertion of the internal pterygoid and extending some distance. 



In the Tragulidse we found (21) the usual attachments from the 

 paroccipital to the mandible and a very slight central tendon, while 

 in Kinberg's specimen (20) the central tendon was evidently longer 

 and the anterior belly attached to the third quarter of the lower 

 border of the mandible, i. e. just behind the middle. 



In the Cervida? (25, 27, 28) the central tendon is very distinct, 

 but, as in all the preceding animals, there is no attachment to the 

 hvoid bone. In Cariacus rvfv.s (27) the two anterior bellies are 

 connected by a muscular layer supplied by the mylo-hyoid nerve. 



In the Bovidfe (32, 35, 36, 39, 40, 42, 43, 45, 47, 49) the central 



