180 THE ACTION OF THE LIVING CELL 



termine the resistance of the fetus both before and 

 after birth. Similarly the development of the fetus in 

 the body of the mother must alter her internal environ- 

 ment. The latter fact is easily made apparent in the 

 various anatomical and physiological changes which 

 accompany pregnancy, and by the vomiting and other 

 evidences of toxemia frequently to be observed. 



Such unpleasant effects, which are commonly ob- 

 served in women and higher animals during preg- 

 nancy, may in part be ascribed to the action of cytost 

 liberated from the uterine tissues as a result of the 

 activities of the developing fetus. For the first week 

 following insemination the developing egg is a free 

 body, but later attaches to the uterine wall. In the case 

 of the monkey, the changes incident to this attachment 

 have recently been described by Hartman (1931). 

 According to this author the embryo of the monkey 

 begins to implant itself in the tissues of the mother 

 about eight or nine days after fertilization, and even- 

 tually becomes half buried in the uterine wall. Hart- 

 man's experiments show that this implantation is ac- 

 companied by an erosive action which for a time 

 causes the maternal tissues literally to "melt away" 

 before the egg and thus affords a mechanism for the 

 attachment of the egg. 



The "melting away" of the mother's tissues, as Hart- 

 man terms the process, is undoubtedly autolysis — the 

 usual procedure by which cells disintegrate. It seems, 

 therefore, that some secretion of the egg must act as a 

 trigger which initiates such autolysis and thus permits 

 implantation to take place. Such an autolysis, in com- 

 mon with any other, must liberate cytost into the circu- 

 lation of the mother and cause her to show the effects 



