76 



KNOWLEDGE. 



[April 1, 1891. 



respectively. Though the comma baciUus of Koch, like 

 the majority of organisms, grows best on an alkaline 

 medium, yet the surface of a potato is acid, and on this 

 it is well known to flourish at the temperature of the 

 blood." 



Those bacteria are everywhere, in the air we breathe, in 

 the water we drink, in the ground we tread on, but 

 hapiiily some are innocuous ; and the noxious mvrst find a 

 suitable soil in which to develop their evil nature, other- 

 wise the human race must have been exterminated by 

 them long ago, and the whole of the animal and vegetable 

 world must have become simply putrefactive media for the 

 propagation of micro-organisms. We cannot pretend in 

 this article to go into any scientific description of the 

 numerous bacteria which, thanks to the researches of 

 Koch, Pasteur, and many other zealous workers on the 

 Continent, have become as well known as creatures of 

 larger growth ; but we will endeavour to point out some 

 of the points of interest to the general public in this new 

 science, as brought before us in the Manual of Bacte- 

 rioloi/!/ of Dr. Crookshank, one of our chief English 

 workers in this branch of science, who established a 

 bacteriological laboratory at King's College, in which many 

 elaborate investigations are carried on daily. WtsMamial 

 is primarily for the use of students, and therefore deals 

 largely with the methods of cultivation, and preparation 

 for the microscope, of the various species of bacteria, all 

 the necessary apparatus being elaborately illustrated. 



The study of bacteria may be considered to be quite recent, 

 yet, as Dr. Crookshank points out, " Leeuwenhoeck, two 

 hundred years ago, recognised and described microscopic 

 organisms in putrid water and saliva, which probably 

 correspond -nath organisms such as vibrios and leptothrix 

 of modern times." The article upon " Medicine " in the 

 Emi/clojxedia Britannicu also points out that Schiinlein 

 "made in 1839 one discovery apparently small, but in 

 reality most suggestive, namely, that the contagious 

 disease of the head called favus is produced by the growth 

 in the hair of a parasitic fungus." In this may be found the 

 germ of the startling modern discoveries in parasitic diseases ; 

 and it seems that even as early as 1773 JMiiller suggested 

 a classification of these microscopic organisms ; but even 

 to the present day their exact place in the economy of 

 nature has not been determined. " Existing as they do," 

 says Dr. Crookshank, " upon the very borderland of the 

 vegetable and animal kingdoms, not only have they been 

 transferred fi-om one to the other, but even the question 

 has been raised whether the smaller forms should be con- 

 sidered as lidng beings at all." But he says: "The 

 gradual improvements in the means of studying such 

 minute objects, the methods of cultivating them artificially, 

 and of studying their chemistry and physiology, and the 

 ever-increasing revelations of the microscope, have resulted 

 in establishing these microscopic objects as members of 

 the vegetable kingdom, ranking among the lowest forms 

 of fungi." 



After showing the various classifications of these 

 fission-fungi. Dr. Crookshank divides them, after Zopf, 

 into four groups, and each group again into genera and 

 species. He then gives a long list of each, classifying 

 them according to their association with disease in man 

 and animals, and adding to thelist such asare unassociated 

 with disease. Glancing at these lists, we are struck by 

 the fact that in some of the groups almost all the species 

 are associated with disease, whOst some forms are common 

 to men and animals. In Sirtjitoiomts, for instance, there 

 are seventeen species traceable to disease in man, eleven 

 belonging to disease in animals, two common to animals 

 and man, and only four unassociated with disease. In 



Sarnjia, on the contrary, all the species appear to be 

 innocuous. In other groups the hurtful and innocent 

 species are more equally di\'ided. In the genus Muio- 

 cocciis, to which belongs the much-dreaded germ of rabies, 

 and also that of scarlatina, measles, and whooping-cough, 

 there are ten species belonging to human disease, five to 

 animals, one to plants, and eighteen which are harmless. 

 In the Bacteriaceffi the hurtful and innocent species seem 

 also to be pretty equally divided ; bitt to this group belong 

 some of the most dreaded of disease-germs, such as that 

 of pneumonia, diphtheria, chicken -cholera, the disputed 

 comma bacillus of Asiatic cholera, the bacilU associated 

 with typhus fever, with anthrax, with tuberculosis, with 

 malaria, with swine fever, &c. &c. 



The yeast-fimgi and mould-fimgi, some of which are 

 so destructive to vegetable life, appear to be allied to the 

 bacteria or fission-fungi, but are nevertheless quite distinct. 

 The moulds of various kinds, which form on almost everj-- 

 thing eatable, especially in damp weather, belong to these, 

 but they also include the potato-blight (PeronoKjiam 

 infi'stinis), grape-disease (Oiflium), the mildew, smut, and 

 other wheat-diseases, the salmon-fungus, and the silk- 

 woiTn disease ; all of which have had disastrous eft'ects 

 upon the prosperity of mankind, although they have 

 not been inimical to human life in the same way as the 

 Bacteria. 



It would seem as though these micro-organisms were 

 Nature's favoured weapons of destruction — her tiny 

 poisoned arrows, with which she shoots hither and thither 

 continuously, and against which all living things, whether 

 animal or vegetable, require to be rendered more in- 

 vulnerable than Achilles. Is there to be found any Styx 

 wherein mankind ni'iy be rendered invulnerable to the 

 attacks of these invisible foes '? Pasteur is supposed to 

 have discovered the means of depriving some of these 

 arrows of their deadly power by extending to other diseases 

 the system of inoculation, introduced first in connection 

 with small-pox, and afterwards modified by -Jenner into 

 vaccination, long before the discovery of Bacteria as 

 the constant accompaniment, if not the actual source, of 

 disease. 



The two diseases, with the cure or prevention of which 

 the name of Pasteur will be always associated, are rabies 

 or hydrophobia, and anthrax, known also as splenic fever 

 or wool-sorter's disease ; the former is, without doubt, one 

 of the most terrible of maladies, and the latter, although 

 less generally known, has caused the cruel death of mul- 

 titudes who have been brought into contact with it. Both 

 diseases are commimicated in the first place from animals 

 to man. The mode of prevention adopted by M. Pasteur 

 is inoculation with the bacillus of the disease, thus re- 

 sembling the old inoculation ior small-pox rather than 

 vaccination, which is the communication of an allied 

 animal disease rather than the human form of that 

 disease. But M. Pasteur does not, as in the old inocula- 

 tion , give the disease in its full force ; but he takes the 

 bacillus, cultivates it in different media, and only intro- 

 duces it into the animal or human body after it has been 

 attenuated and its full malignity destroyed. 



Speaking of anthrax. Dr. Crookshank says: " By cul- 

 tivating the bacillus in neutralized bouillon at 42°-43° C. 

 for about twenty days, the infecting power is weakened, 

 and animals inoculated with it are protected against the 

 disease." To obtain a still more perfect immunity, they 

 are inoculated a second time with material which has 

 been less weakened. The animals are then protected 

 against the most virulent anthrax, but (nily far a iiiiii\ 

 From such a culture, however, new cultures of %arulent 

 bacilli can be started, and a culture that is "vaccin" for 



