1S84.J The Significance of Human Anomalies. 
6 67 
great principle of Evolution, the explanation of these varia- 
tions is simple enough, viz., that they point to the fadt that 
man has descended from some lower form, and “ is the co- 
descendant with other mammals of a common progenitor” 
(Darwin). 
Again, many structures which in man are merely rudiments 
and quite useless, nay, sometimes a source of danger, are 
seen fully perfected in some of the lower animals, and in 
them fulfil a definite purpose. The existence of such rudi- 
mentary organs (or, as Haeckel calls them, “ worthless 
primeval heir-looms ”) as the ear-muscles, the appendix 
vermiformis in the intestines, the thyroid gland, the remnant 
of the third eyelid, the rudimentary tail-bones, and many 
others, is not satisfactorily accounted for on the theory of 
the plan of general unity ; but if we look upon them as 
parts which have become funCtionless and atrophied from 
want of use, and by heredity have been transmitted from 
generation to generation, a bright light is thrown on the 
reason of their existence. In the present paper I do not 
intend to. dwell on the significance of rudimentary organs 
which exist normally in man, but shall confine myself to 
those structures which occur as variations. 
I might here mention that some parts, as for instance 
certain muscles of the thumb, occur in man, but not in the 
lower animals ; these we may take as indications of the 
advance of man to a still higher development. 
To the study of embryology we owe much in elucidating 
many morphological problems, and removing others from 
the . domain of theory. By our knowledge of this most 
intricate subject the significance of many variations and 
rudimentary organs is made plain. 
It has been well said that “ the development of the indi- 
vidual is the compressed development of the race in the 
process of compression ; some features are suppressed or 
modified, and others are thrown into relief.” In the deve- 
lopment of the embryo we see the history of the race, but 
the higher the form the more quickly does the embryo pass 
through those stages and transformations which are the 
equivalent of what is persistent in types below. In lower 
forms these stages are much less rapid, and in faCt are true 
metamorphoses. The changes occurring in the development 
of the common frog will furnish a familiar example of this 
latter statement. The more we know of embryology the 
more the truth of the saying that “ development means 
descent ” is apparent. 
It may not be generally known that no two individuals 
2 Y 2 
