144 THE GENERAL ANATOMY OF THE CERCOPITHECIDAE [SECT. A 



II. Contribution from the second thoracic nerve. 

 Man : variable, and usually small. 



Cercopithecidae : variable but often large (cf. Fig. 89). 

 From these data (i and il), it appears that the plexus in the Cerco- 

 pithecidae tends to a position more distal than that of Man. 



A similar conclusion will be drawn from the study of the 

 lumbar or of the sacral plexus in the several forms. Here it will 

 suffice to record the evidence of the N. femoralis (anterior crural 

 nerve). 



Tupaia (an insectivore) : 17,18. (Leche 4 .) 



In the lumbar plexus, the process of reduction in the number 

 of thoraco-lumbar vertebrae is doubtless influential so far as Man 

 is concerned, but this factor must be excluded in the case of the 

 brachial plexus. An appeal to modifications induced by the erect 

 attitude has been deemed reasonable if not sufficient, but of late, 

 objections have been brought against this explanation by Professor 

 Wingate Todd. 



However this may be, the various members of the Primates 

 fall into a sequence when judged by the test as applied to the 

 lumbar plexus, and the sequence is identical with that considered 

 on a summary of the whole evidence to be the natural one. 



Before passing from the nervous system, it should be added 

 that the Cercopithecidae (or at least those in which the tail is 

 long) agree with other long-tailed mammals in the possession of 

 well-marked coccygeal or caudal nerves concentrated in a long 

 "collector" nerve on each side of the tail. 



1 Quoted by Kohlbrugge, op. cit. - op. eit., cf. p. 143 supra. 



3 Morphologisches Jahrbuch., Band xviii. 



4 Quoted by Huge, op. cit. 



