Opinions on Epidemics and Epizootics. 287 



resembling yeast, and many of them taking the beaded, or 

 bacterium form, are capable of setting up a variety of fermenta- 

 tions, eacli developing particular products. M. Davaine has 

 apparently traced a splenic disease in sheep and other animals 

 to an organism of this sort, and the counter experiments seem 

 to show, not that he was wrong, but that his opponents 

 were not operating with the particular organism of which 

 he spoke. Any small independent body, whether having 

 distinct walls or not, which contains or consists wholly 

 or partly of germinal matter, capable, under appropriate 

 conditions, of multiplying by reproduction, may be con- 

 veniently called a cell. Such cells may be able to live and 

 multiply in more forms than one. Indeed, as we proceed 

 downwards in the chain of life, the tendency to variation 

 appears decidedly to increase. If, therefore, it is thought 

 probable that zymotic disorders can arise from cells of a par- 

 ticular sort floating in the atmosphere, we should not be 

 justified in asserting that wherever and whenever such cells 

 thrive and germinate in a living being, they must produce one 

 constant type of disease. The proof that a small-pox cell, 

 taken from a pustule, and introduced into the blood of a fit 

 subject, reproduces in him the same disease of small-pox, is 

 not tantamount to a proof that germs from small-pox cells, if 

 such exist, floating for an indefinite time in the air, must 

 either reproduce small -pox, or exert no morbid action at all. 

 We have no proof that germs of disease admit of no variation 

 in their development, whatever may be the conditions under 

 which they are placed. We neither affirm nor deny the accuracy 

 of different hypotheses ; our object is to explain, and, if pos- 

 sible, to enforce something like scientific accuracy in reasoning 

 upon these subjects, and to put our readers upon their guard 

 against the pervading error of considering things proved that 

 in reality are only surmised. 



In reference to those opinions concerning the cattle disease 

 which bear a strong family likeness to similar opinions con- 

 cerning other diseases, now known to have been nothing better 

 than the offspring of fear and superstition — it is necessary to 

 determine the special kind of test to which they should be 

 subjected. In the first place, the importation theory should 

 be cautiously sifted. In every case in which it is assumed 

 that the disease was caught through contagion, proof should 

 be demanded, first, that the alleged circumstances under which 

 the contagion is stated to have operated did really exist ; and, 

 secondly, that such circumstances were really competent to 

 produce the effect. In one case reported in the daily papers, 

 the only mode of supporting the importation and contagion 

 theory was by presuming that the poison matter might have 



