CONTAGIOUS DISEASES OF DOMESTICATED ANIMALS. 415 



magnifying power is used, a Tolles jV? for instance, can sometimes hard- 

 ly be distinguished from the hitter, except by its livelier movements, 

 which, of coiu'se, cannot be shown in a drawing. Two or more species 

 of Schizomycetes may be very simihir in appearance, or so nearly alike 

 as to make a discrimination impossible, and still they may possess en- 

 tirely different properties, and produce very different effects. The fol- 

 lowing may serve as an illustration : The pigment-bacteria, or cliromo- 

 genic spliaerahacteria of Cohn, are all alike and cannot be distinguished, 

 and still the various species i^roduce different colors, but each species 

 invariably the same. One, for instance, produces green, another red, 

 another blue, another orange, and so on. The Schizomycetes of swine 

 plague and those of putrefaction, though similar in form, are entirely 

 different in their effect, and even antagonistic to each other in so far as 

 the former, as has already been stated, commence to disappear as soon 

 as the latter make their appearance. To show the ^asible difference be- 

 tween the swine plague Schizomycetes and Bacterium tenno I refer to 

 drawing, Fig. XIX a and &, which represents the latter after Siedamgro- 

 tzky and Cohn. 



Not all the small particles, however, which are sometimes seen swim- 

 ming in the blood or blood serum, and may even shovr a slight motion, 

 are micrococci, or globular Schizomycetes; some of them are products 

 of detritus, or minute fat globules, &c. But those minute globular 

 bodies, which strongly reflect the light, are sometimes even more nu- 

 merous than the blood-corpuscles, and are not destroyed by adding a weak 

 solution of caustic potash, must be considered as micrococci, or globular 

 Schizomycetes. Further, where clusters or colonies [gliacoccos or zoo- 

 gloea-ma-sses) are existing, and where rod-shaped Schizomycetes or bac- 

 teria are accompanying the spherical forms, then no doubt can remain. 

 There are yet several other means by which their tnie nature can be 

 determined, but to enumerate them would lead too far, and will not be 

 necessary. One other point, however, may yet be mentioned. If the 

 small globular bodies, seen under the microscoi)e, are detritus or min- 

 ute fat-globules, they will, at best, remain as they are, but will not 

 propagate or increase in numbers like the micrococci, which multiply or 

 propagate in many other fluids besides blood, if put into them, and even 

 in fluids entirely different from that in which they have been found. In 

 other words, the micrococci can be cultivated, and detritus and fat- 

 globules cannot. 



Under some circumstances the swine plague Schizomycetes are easily 

 destroyed, for instance, if exposed on a bare, dry surface to the rays of 

 light, or a free access of air ; but in a suitable vehicle or nutritious sub- 

 stance, or protected by a porous body which keeps them moist and 

 warm, their tenacity of life seems to be very great {cf. experiment with 

 experimental pig No. 3, and the case communicated by Mr. Pendarvis). 

 It is also a well-known fact that in the spring, particularly if a hard or 

 dry winter has been destructive to the infections principle, swine plague 

 almost invariably makes its first appearance again in swine-yards which 

 contain old straw-stacks, «&c., at the edge of the timber, or in some other 

 sheltered nook or corner where the Schizomycetes have found protection. 

 As to a proper vehicle or nutritious substance or fluid, the Schizomyce- 

 tes of swine plague do not seem to be as particular as many other kinds. 

 Water, especialiy if it contains a slight admixture of organic gu])stan- 

 ces, is about as suitable as anything else. 



The swine-plague Schizomycetes, even in a very sick animal, or in the 

 carcass of one that has just died, are never as numerous in the (fresh) 

 blood as in the morbid products, the urine, the excrements, the lymph, 



