U5 



ble to determine, and concerning the causes which bear on their 

 production we know little. I have found them more commonly on the 

 right side than on the left, and in females more frequently than in 

 males. The influence of sex in determining the occurrence of anomalies 

 is probably, however, very slight; for though in my notes I find that a 

 considerable preponderance of the cases occurred in females (as a greater 

 number of individuals of this sex are submitted to our observation in the 

 dissecting room), yet others have remarked the contrary ; and it is proba- 

 ble that, had we a sufficient body of evidence, we would find the numbers 

 tolerably equal in both sexes. I can in general concur fully with the 

 introductory remarks of Mr. Wood, in his admirable papers on this sub- 

 ject, in the " Proceedings of the Royal Society" for 1865. 



The varieties which I am about to notice may be arranged into six 

 classes : — 



1st. Such as arise from the presence of muscles not typical parts of 



the human frame ; 

 2nd. Variations of normal muscles by duplicity, either in whole or 



in part ; 



3rd. Variations of normal muscles by complexity or alterations of 



attachment, of course, or of arrangement ; 

 4th. Variations by the coalescence or union of muscles normally 



separate ; 



5th. Variations by segmentation, or the fission of muscles into several 

 parts ; 



6th. Variation by suppression, either partial or complete. 



This arrangement, it will be seen, is an extended modification of 

 that adopted by Mr. Wood, and for practical purposes will be found 

 extremely convenient. 



I. The first, and most interesting group of anomalies comprises all 

 those muscles which are occasionally present, as if by accident, in man, 

 although not normal constituents of the human frame, either in rudi- 

 ment or in perfection. Most, if not all, of these are natural elements 

 existing in lower animals ; and when they occur in man, they are usually 

 unconnected with his normal muscles. In some of the instances in 

 which I have noted them, they were gregarious in their occurrence, two 

 or more anomalies of this class being present in the same individual, 

 and in the majority of instances they were symmetrical. 



The following are the principal varieties of this class which I have 

 observed : — 



1. Sternalis rectus I have seen many times, varying in its degree 

 of development, from a few vertical fibres or tendinous bands running 

 in front of the sternum, either from the sternal tendon of the sterno- 

 mastoid, or from the manubrium, to its full perfection, as a large fleshy 

 mass, separate from both rectus abdominis and sterno-cleido- mastoid. 



R, I. A. PEOC. VOL. IX. 3 N 



