ee BIOLOGY AND SOCIAL PROBLEMS 



equivalent of an egg and justified the phrase 

 used in the earlier part of his treatise and so 

 often associated with his name, " Omne vivum 

 ex ovo," every living thing from an egg. To 

 this declaration, as Harvey explicitly states, 

 the human being is no exception. But it was 

 not vouchsafed to Harvey to see the egg of 

 man or of any other viviparous animal except 

 dimly in his mind's eye. 



The egg of the mammal was discovered late 

 in the spring of 1827 by Von Baer. The first 

 egg seen was that of a dog, but subsequently 

 the eggs of other mammals, including man, 

 were found, and an account of the whole re- 

 search was published in the latter part of that 

 year. This matter-of-fact statement of an in- 

 vestigation, the repetition of which would be 

 a simple affair in the hands of even an elemen- 

 tary student to-day, gives no idea of what it 

 cost its discoverer. In his autobiography Von 

 Baer speaks of the physical strain and damage 

 to health from the long hours he spent over 

 his microscope and his worktable, and because 

 of his reluctance to leave his workshop, he com- 

 pares himself to a hermit crab. "And so it 

 happened," he says, " that in the course of a 

 year, I shut myself up in my shell while the 



