116 ANIMAL LIFE AND HUMAN PROGRESS 



which make only an occasional appearance in the rest of the 

 Primates. The insertion of the human pectoralis minor to the 

 coracoid process is, contrary to the usual teaching, a feature 

 in which Man shows a more primitive arrangement than that 

 seen in any of the Primates except the anthropoids. As 

 human specialisations we may note the presence of the 

 peroneus tertius, the plantaris and the serratus posticus 

 inferior, and again we cannot fail to be astonished at the 

 remarkably early differentiation in the embryo of such a 

 distinctly human character as the peroneus tertius. Of 

 Primate specialisations not normally developed in Man we 

 may cite the acromio-trachelian and the dorsi-epitrochlean 

 muscles. 



Of these muscles the pectoralis minor, the deep head of 

 the pronator radii teres, the pyramidalis, and several others, 

 are of particular interest, since, when Man more nearly 

 resembles the anthropoids and differs more widely from the 

 lower Primates, it is in the display of primitive features, 

 which are lost in the monkeys, retained occasionally in the 

 anthropoids, and preserved as normal features in Man. This 

 is a point which needs particular emphasis ; for the great 

 bulk of the teaching concerning such structures has been 

 formulated along the lines which were laid down by Huxley 

 and to which I have already referred. If, upon these lines, 

 the phylogeny of such a muscle as the pectoralis minor is 

 sought, the human condition is contrasted with that of the 

 anthropoid, and this in turn with that of the monkeys and 

 lemurs, and this again with the arrangement present in a 

 typical quadrupedal lower mammal. In this sequence a 

 steady gradation is often displayed, and by orthodox teaching 

 we are led to believe that the human condition is the more 

 specialised that it is the outcome of evolutionary stages seen 

 in the making in the bodies of the animals examined. But 

 one needs to go deeper than this, and to seek the muscle in 

 the more generalised reptiles, in the Prototheria, and general- 

 ised Metatheria. When this is done a very different picture 

 presents itself ; for we find that the human condition is most 

 primitive, that the anthropoid apes retain at times a nearly 





