STEUCTURE OF DOMESTICATED AXIMALS. 293 



reproduction; but less than fifty years ago, a German physi- 

 ologist, Karl Ernst von Baer, one of the ablest investigators 

 of our century, made the astounding discovery that all ani- 

 mals bring forth eggs that may not be distinguished from one 

 another at a certain stage ; that all our cattle, all our domesti- 

 cated animals, all the beasts of the forest, as well as all the 

 birds on earth, produce eggs similar to one another. This 

 seems a very extraordinary statement, yet perhaps I shall be 

 able to make you familiar with the fact, and to make you under- 

 stand it as fully as you know that your hens lay eggs. But the 

 eggs of a great many animals most useful to us, and of those 

 about which wx would like to know most, have not been 

 studied microscopically. I have devoted a great deal of my 

 life to similar topics, and I have never yet seen the egg of a 

 mare ; I have never yet seen the egg of a cow ; I have never 

 yet seen the egg of a pig ; yet I believe that these animals 

 brino; forth eijsrs as much as the animals that have been investi- 



O CO 



gated with reference to that point. A suflicient number of 

 quadrupeds have been studied to leave no doubt that all quad- 

 rupeds produce eggs as well as birds, as well as all other 

 animals, without exception. One of the ablest physiologists 

 of our time, Professor Bischoflf, of Munich, has devoted over 

 twenty years of his life to the study of a few of these animals, 

 and the results of his investigations are embodied in a volume 

 of many hundreds of pages, with a large number of plates, 

 representing the history of only four species of quadrupeds. 

 One is the rabbit, another is the clog, a third is the guinea- 

 pig, and the fourth a species of deer which is common in the 

 forests of Europe, — the roebuck ; and the history of these 

 animals, as presented in this volume, covers only the very 

 earliest period of gestation, — and mainly that portion of their 

 history embraced during the first days of gestation, during the 

 time when the egg of these animals is transformed into a germ 

 w^hich grows to be an animal like the parent. Now, unless 

 we can have a similar history of any one of our more valuable 

 domesticated animals, as of the horse, or of the cow, we can- 

 not expect to know how to influence their reproduction. This 

 is the very foundation of all knowledge in that direction. 

 What will be necessary for that? When these investiga- 

 tions began they were made upon animals which could be 



