QUADRUtfANA. 7 



while the fore-feet or hands are in search of a hold below, the hind- 

 feet are holding on above. 



It would appear in some instances, that a thumb on the hind-foot 

 was of more service than on the fore ; for in the opossum the thumb is 

 placed on the hind-foot, and the corresponding toe on the fore-foot is 

 similar to that in many common animals, as the raccoon, rat, &c. 



This situation of thumb must assist greatly in climbing, especially 

 when assisted by the tail, which answers to a third leg ; from which 

 we may observe that the holding, and the points from whence certain 

 motions are derived, are behind. These three parts being fitted for 

 alternate motion and holding, fits them very well for sitting erect ; a 

 position probably they give suck in ; and if this operation is performed 

 in a tree, it appears very necessary. 



Of the Brain of a Monkey. 



The dura mater in a monkey does not adhere to the pia mater along 

 the longitudinal sinus, but by means of veins of the pia mater. The 

 veins pass into the sinus, some at a right angle, others at acute angles, 

 with regard to the current. There is no 'additamentum' [cornu posterius] 

 to the ventricle. The corpus striatum is more rounded, and does not 

 pass so far back over the thalamus. The thalami are more united. 

 The cerebellum sends two lateral processes of dura mater, and above 

 the seventh pair of nerves. The medulla oblongata is more flattened. 

 The optic nerves unite nearer the foramen opticum than in the human. 

 The pineal gland is smaller in proportion, and lies quite between the two 

 testes [hinder bigeminal bodies], which are larger in proportion. The 

 vertebral arteries have a small canal of communication going between 

 them. 



[The Chimpanzee {Simla Troglodytes, Blum., Troglodytes niger, 

 Geoffr.).] The Or an Utan, sent from Sierra Leone by Mr. 

 Dubois. 



This animal was a young one : its mother was shot. Mr. Afzelius l , 

 who brought it home, said there were many, and which were near 5 feet 

 high. She fell, when shot, from a tree ; and in the fall still held the 

 young one to her, which also brought it down, and in the fall it broke 

 its arm. 



1 [Dr. Adam Afzelius, a Swede, born in 1 750, was a pupil of Linnieus : he made a 

 voyage to Sierra Leone in 1792, and Sir Joseph Banks became possessor of part of 

 his Natural History collections. In 1796 he was Secretary to the Swedish Embassy 

 n London, and in 1812 was made Professor of Materia Medica at Upsal.] 



