IMPREGNATION 261 



which one fluke may produce. The whole story sounds like a fairy tale; it 

 is, however, a true story every whit. 



Only less marvellous is the history of the generation of the tape-worm, 

 which in every mature joint produces myriads of eggs, each containing a 

 living embryo, globular in form and armed with six minute hooklets, which 

 have a purpose presently to be divulged. Mature joints or segments are 

 constantly being expelled from the intestines of infested animals, lambs, for 

 example, and are, as a matter of course, eaten with herbage by other graz- 

 ing animals. Reaching the digestive organs of the warm-blooded animal, 

 the eggs are set free, the armed embryos find their way, by the aid of their 

 hooklets, to certain organs, lungs, liver, or brain, fix themselves securely 

 by the little hooks, and grow into water-bladders (hydatids), sometimes of 

 great size. In the interior of the hydatid there are to be found numerous 

 minute germs, sometimes the numbers cannot be estimated, which are 

 in reality tape-worm heads and necks, ready to grow joint by joint, until 

 they reach several feet or yards in length. The hydatid is swallowed by a 

 dog or other carnivorous animal, and tape-worms are again developed. 



These two examples of alternation of generations may suffice. Ob- 

 viously the scheme has enormous advantages on the side of multiplication 

 of species with an abnormal rapidity, and it is a startling reflection that 

 the creatures thus liberally distributed over the world are destined in 

 their struggle for existence to inflict disease and death on creatures 

 higher in the scale of creation than themselves, undiscovered, even 

 unsuspected. 



PHYSIOLOGY OF GESTATION AND PARTURITION 



IMPREGNATION 



Successful horse-breeding demands a special knowledge of horses, so far 

 as concerns their external conformation, aptitudes for different services, and 

 peculiarities and defects; and in its practical aspect it requires also a sound 

 knowledge of horse -rearing and management, particularly of the young 

 stock, and of mares during pregnancy and parturition, and for some time 

 after that event. Constant care and attention are likewise needed on the 

 part of those entrusted with the carrying out of the details of breeding, 

 in order to avoid accidents and ensure a satisfactory result. 



The age at which horses commence to breed depends to some extent 

 upon race peculiarities and external conditions, which have an influence in 



