MUSCULAR SYSTEM 
As might be expected, we find, in the 200 to 250 muscles 
which form the active motor apparatus of the human body, 
variations far greater and more numerous than any already 
described in the different parts of the skeleton. 
It may confidently be asserted that hardly a single human 
subject has been examined which has not shown some variation 
or other in the muscular system; and in a great number of 
bodies new muscles are discovered which have not before been 
observed, and of which no mention can be found in text-books. 
Considering this “embarras de richesse,’ we may be excused 
for entering in the following pages somewhat into detail; it 1s, in 
fact, absolutely necessary to do so in order to get a general idea 
of the immense mass of material available. Of the extent of this 
variation an approximate idea may be obtained from the fact 
that my French colleague Testut, in his work of 900 pages on 
the muscular anomales in Man, has by no means exhausted the 
subject. 
Examples will be considered in the following order :— 
(1) Retrogressive or vestigial muscles. 
(2) Muscles which, appearing only occasionally, are considered 
to be atavistic. 
(3) Progressive muscles. 
This order cannot be rigidly adhered to, inasmuch as both 
progressive and retrogressive development have been observed to 
take place, side by side, in one and the same muscular region. 
It is further to be noted that those muscles: which are actually 
progressive as far as the genus Homo is concerned, are not recog- 
nisable as such in mere individuals; their anomalous conditions 
can only be considered as individual variations until traced 
through successive generations, 2.e. until it is proved that they 
are inherited. 
An accurate knowledge of Comparative Anatomy and Ontogeny 
H 
