CONSPECTUS OF ORGANS MENTIONED IN THE TEXT 205 
On glancing through this summary, it will be seen that the 
arrangement of the subject matter is not altogether a natural 
one; indeed, in introducing it, I have only sought to give a 
classified survey of the contents of this book. 
Physiological considerations must determine the ultimate 
method of grouping the facts, especially because, as was pointed 
out in the introduction, the term vestigial is, as a rule, 
only applied to such organs as have lost their original physio- 
logical significance. Retrogressive organs, on the contrary, are 
such as may still remain functional, though, as a rule, only to 
a limited extent. It has further been seen that both these 
conditions in the process of degeneration may be, in different 
individuals, realised in one and the same organ. The palmaris 
longus and plantaris muscles furnish a case in point; for while 
these, and especially the former, are not infrequently so well 
developed that there can be no doubt of their being functional, 
cases occur in which one or the other of them has become quite 
transformed into tendinous tissue and really vestigial. And in 
yet other cases these muscles may altogether have disappeared. 
On this subject Osborn makes the following appropriate remark :— 
“Both in the muscular and skeletal systems we find organs so 
far on the down grade that they are mere pensioners of the body, 
drawing pay (ve. nutrition) for past honourable services without 
performing any corresponding work—the plantaris and palmaris 
muscles for example.” ! 
Many similar examples might be given. Confining our 
attention to muscles alone, it may suffice to recall the pyramidalis 
and certain muscles of the head. 7 
1 Cf. this author’s Cartwright Lectures, Lect. I. ‘‘ The Contemporary Evolution 
of Man,” Medical Record, Feb. 20, 1892. 
