PAKASITES OF ANIMALS. Ig7 



Again, most of us have observed, wriggling- in some puddle, a 

 long thread-like worm, known commonly as the horse-hair worm, 

 so named from the popular notion that they are in fact but trans- 

 formed horse hairs ; and so confident are some good people in 

 every community that this belief is correct that they are quite 

 eager to assure us that they, or their fathers, have watched the 

 entire process of transformation, and hence there can be no doubt 

 about it. This being admitted, it is easy to suppose that conditions 

 might frequently exist which would favor the genesis of similar 

 organisms in the bodies of animals while yet living. With the 

 purpose of determining if possible the truth or fallacy of this 

 hypothesis,- many observations and experiments have been made 

 by investigators whose skill and general accuracy are admitted. 

 Pasteur's researches on fermenUtiou have led him to conclude 

 that the phenomena of fermectf.t'.oa Bod putrefaction are dependent 

 on the presence of an aniacial ivTz^sut of tha genus Vibrio ; and he 

 regards each of the five or sii knoTrn species of this genus as 

 having the power of producing a special kind of putresence. If 

 a putrescible liquid, containing air in solution, be hermetically 

 sealed up in glass vessels and left to itself, minute infusoria at 

 fii'st appear, to which the names monads and bacteria are given. 

 These absorb the oxygen and give out carbonic dioxide. When 

 the oxygen is exhausted they die ; but if the germs of the vibrio 

 chance to be present, as is most likely, they find in this liquid, thus 

 freed from oxygen, in its uncombined state, the proper conditions 

 for their growth. With their development putrefaction commences. 



But if the putrescible liquid be freely exposed to the air, the 

 monads and bacteria are at first developed in such numbers that 

 they form a pellicle over the surface of the liquid, which is 

 constantly renewed, and thus the oxygen is entirely absorbed and 

 its entrance into the liquid wholly prevented. Then the vibrios 

 begin to be developed and putrefaction commences. 



Professor Wyman undertook, some years since, a series of 

 experiments in order to determine whether germs, which might be 

 presumed to be so minute as to escape observation, were actually 

 present in all cases where putrescence occurs, before its inception. 

 His mode of experimenting in general resembled that employed by 

 Pasteur, but greater pains were taken with the details. Liquids 

 containing various infusions were boiled, and then sealed without 

 contact of air, save such as had been admitted through tubes heated 

 to redness. The results were far from decisive, not warranting 



