THE INHERITANCE OF ACQUIRHMKNTS 77 



Wc have already seen that it is iiupossiblo to re- 

 concile Weismaun's theory of the continuity of the 

 germ-plasm with the transmissibility of such local 

 changes as ordinary injuries or mutilations. Neither 

 the blood-stream nor the existence of " internal secre- 

 tions," nor the nervous connections of the reproduc- 

 tive glands, helps us to conceive how a burn that 

 destroys the skin of the father's back, let us say, can 

 lead to the formation of a scar on the back of his 

 child.i 



But the fact that certain glands produce " internal 

 secretions " which pass into the blood and intluence 

 the rest of the body has been utilised as suggesting 

 an hypothesis which may be of value. In every case 

 where an organ or tissue produces a "specific secre- 

 tion," that secretion may be conceived as having a 

 specific action upon those "determinants" in the germ- 

 plasm which are destined to give rise to the corre- 

 sponding organ in a new individual. Dr. Vernon, 

 who accepts this hypothesis, says : " It is almost in- 

 conceivable that each spot of skin on the body, or 

 each finger, should have a specific secretion, and that 

 an injury to it, by changing its secretion, should so 

 aflfect the germ -plasm as to produce a similar change 

 in the corresponding area of skin of the finger of the 

 offspring"; but he is prepared to adduce the hypo- 

 thesis of specific secretions in a large nundier of 

 cases, such as injury to, or feeble develo]imont of, 

 the brain, active exercise of the muscles, and so 

 forth, where the belief in the existence of any 

 specific secretion is entirely unsupported by any 

 recorded observations. In such cases it is as yet 



1 It is not asserted that this occurs 1 



