Bacteria have also been found in the blood during measles, and in the splenic apoplexy of sheep and cattle. They have likewise been identified in diphtheritical exudations both from the kidneys and womb, as well as in the blood during an attack of rheumatic fever, and
they are undoubtedly present in the same fluid during many feverish disorders. Drs Lewis and Cunningham failed to discover them in the blood of cholera patients. Professors Cohn and Koch stand prominently forward as the advocates of the germ theory of disease by bacteria. Professor Cohn divides the bacteria into groups, genera, and species, and assigns to each species a different function.
For instance, he considers the ferment of contagion to be due to the presence of a variety of the sphere-shaped bacterium—one of his groups. He divides the whole group into three—the chromogen, zymogen, and pathogen, the bacteria of pigmentation, of fermentation, and of contagion, respectively. He says those organisms are exceedingly minute, darkish or coloured granules, so small as to be immeasurable. They frequently present the appearance of beaded chains or the form of aggregations. They are motionless and are occasionally found with the Bacterium termo in putrefying organic liquids.
Messrs Chauveau and Sanderson have discovered a bacterium in vaccine lymph which believers in the germ theory class among the pathogen bacteria, and which they have named the Micrococcus vaccinæ. Amongst the pathogen bacteria they also include the Micrococcus dipthericus and Micrococcus septicus, the former found in the epithelium of certain organs during certain forms of pyæmia, and the latter in the miliary eruption of typhus, pyæmia, and other diseases. The chromogen or pigmentary bacteria have occasionally been the means of working miracles. Several instances of bread exuding blood, under supernatural circumstances, are related by Rivola. Ehrenberg found this colour on some bread in the house of a patient who had died of cholera, and he ascertained the pigment to be due to the presence of the Monas prodigiosa, small round bodies which Professor Cohn classes with the micrococci, a variety of the sphere-shaped bacterium.
The recent investigations of Koch were directed to the cause of splenic fever, and Cohn on examining his specimens found that they were examples of Bacteria of the species called Bacillus anthracis, which seems to present little or no difference to the Bacillus subtilis of hay infusions. Koch found that bacilli increase with enormous rapidity in the blood, and in the fluid of tissues of living animals, by developing in length and dividing transversely. The animals employed were chiefly mice, and a small incision being made at the root of the tail, as minute a drop as possible of the fluid containing the bacilli was injected into the system. The spleen invariably became enormously swollen, and filled with a large number of crystalline-looking rods of varying size, never exhibiting movement or spore formation; they increased in numbers solely by division. The number of bacilli found in the blood varies in different animals; thus in the guinea-pig it was enormous, sometimes exceeding that of the blood-corpuscles; in the rabbit much smaller, so that sometimes several drops had to be examined before any were found, in the mouse often nil. In the blood of dead animals or other suitable fluids the bacilli grow to very long straight leptothorax-like filaments (within certain limits of temperature, and with the presence of air), while the formation of numerous spores goes on at the same time.
Kohl believes that it is to the presence of the spores that the occurrence of splenetic fever appears to be referable. When living, inoculation with them always produced the disease; but if killed, as by drying, or a high temperature, inoculation failed; it was necessary either that living spores should be present, or that the filaments should be capable of generating spores, in order that the disease should be propagated by inoculation.
Koch tried whether the poisonous bacilli spores could gain entrance through the digestive organs, but found that mice and rabbits could eat them with impunity. Koch draws attention to the similarity of splenic fever to typhus and cholera. He says it presents analogies to typhus in its dependence on soil-water, its preference for low grounds, its sporadic occurrence throughout the year, and its development into an epidemic in the late summer and autumn. Like cholera, again, he says, it is connected with soil-water, and it also agrees with cholera in the point which has been so well made out by Pettenkofer, that on board ship an interval of three or four weeks is sufficient to prevent its further development.
Hence Koch is disposed to hope that the contagium of typhus and cholera may still be discovered in the form of some Schizophyte or spheroidal bacterium, though practical observers have hitherto sought for them in vain.
Many pathologists, however, refuse to accept the accuracy of these deductions, and regard the presence of bacteria in the blood and tissues during disease as of no significance; whilst they deny that it is satisfactorily proved that they are the cause of disease.
Dr Lionel Beale says:—“Changes in the processes of digestion are soon followed by the multiplication of bacteria in every part of the alimentary canal, and within a few hours countless millions may be developed. They multiply in the secretions under certain circumstances, almost as soon as these are formed, and I have adduced evidence to show that bacteria germs exist even in healthy blood. In the very substance of some cells I have seen them, and in many cases in which little granules have been discerned in connection with bioplasts. There is reason to believe that some of them are really bacteria germs, passive as long as the higher life is maintained in its integrity, but ready to grow and multiply the instant a change favorable to them, and adverse to us, shall occur.”