123 



In the compilation of this table, regard is had to the absolute num- 

 ber of specimens of variety, and not to the number of species of varia- 

 tions in each region ; but it is a matter of experience that the two closely 

 correspond, and muscles which frequently vary are liable to the greatest 

 number of kinds of irregularity. 



This and the succeeding table I have made out from my own 

 observations alone, and thus they may diifer from the experience of 

 others in several respects. However, to form true estimates of these 

 degrees of frequency, the combined experience of many observers would 

 be requisite. In the construction of these tables, I have taken into 

 account all my observations, extending over the Sessions 1859-67, 

 inclusive, and not merely the results of last year's researches. 



As the preceding table indicates the relative order of the occurrence 

 of anomalies in the various regions of the body, so the second list 

 illustrates the frequency of occurrence of the classes of varieties in 

 each region : — 





6 













ti 



a 





rear 



oj 

 o 



o 



i 





o 



03 



O 



I 





o 



03 



% 



M 



< 



© 



Eh 



< 



Coalescence, 



4 



3 



1 



4 



4 



1 



6 



5 



Absence, . . . 



2 



1 



5 



3 



6 



4 



5 



3 



New Germs not nor- j 



3 



6 



2 



6 



3 









mal part of the body ) 













3 



3 



1 



Duplicity, . . . 



6 



5 



6 



5 



5 



6 



4 



6 



Varieties of Course, . 



1 



4 



3 



1 



1 



2 



2 



2 



Fission, .... 



5 



2 



4 



] 



2 



5 



1 



4 



I have not found all classes of varieties more common on the right 

 than on the left ; but I agree with M'Whinnie, that anomalies are more 

 frequently unsymmetrical than otherwise. Some new muscles, as the 

 flexor carpi radialis profundus, seem to occur more frequently on the 

 right side, as the eight instances recorded by Wood (P. R. S., 1867, 

 p. 530; and ''Journal of Anatomy and Physiology," vol. i., No. 1), 

 are all upon that side ; and the three instances in which I have found 

 it are likewise on the right. The rectus thoracicus displays a similar 

 proclivity to the right side. Some other irregularities seem to occur at 

 least as frequently on one side as the other ; thus, I have seen the 

 humeral head of the biceps rather more often on the left than on 

 the right. 



Varieties are, probably, more common in males than females ; those 

 of fission and suppression occur more frequently in the latter, as they 

 usually possess a weaker muscular system. Anomalies of duality, 

 altered course and attachment, and coalescence, most frequently are to 

 be found in males. New muscular germs are more frequently de- 

 veloped in the male sex, although an exception has b een claimed for 

 some. JBochdalek, in speaking of the crico-thyroideus posticus (kera- 



B. I. A. PEOC. VOL. X. s 



