SCHIZOMYCETES. 181 



give rise to malignant pustule: similarly pyaemia, small-pox, diph- 

 theria, and other so-called " contagious diseases " are occasioned by 

 Bacteria of extreme minuteness (Micrococci). l Even in recurrent fever 

 the presence of a spirally twisted Bacterium (Spirillum) in the blood 

 is a constant phenomenon. According to Koch, cholera is also 

 caused by a Bacillus (B. comma). 2 Since our experience of the patho- 

 logical nature of these structures is daily widening, we can understand 

 how many modern pathologists would refer the infectiousness of all 

 such diseases to the presence of active Schizomycetes. The old 

 doctrine of " Contagium vivum" (p. 121) is thus resuscitated in a 

 changed form. 



If we inquire without prejudice into the reasons which lead us 

 to refer the Schizomycetes to the vegetable kingdom, in spite of their 

 animal-like nutrition and locomotion, we can give no other answer 

 than this, that they belong to a phylogenetic series, which leads in 

 uninterrupted succession to indisputable plants. The properties which 

 they themselves possess hardly suggest a reason for separating them 

 from the Protozoa, for the Schizomycetes are organisms of small size 

 and simple structure, without cellular organs or tissues, and with 

 exclusively (or at least predominantly) asexual reproduction. They 

 are, in other words, creatures which in their organization do not (or at 

 most only slightly) transcend the differentiation of a simple cell, and in 

 fact are sometimes mere masses of protoplasm. 



From the phylogenetic point of view, we can not only define the sys- 

 tematic position of the Schizomycetes, but are also enabled to restrict 

 the Protozoa to the three classes of Ehizopoda, Gregarinida, and In- 

 fusoria. These also are, of course, not wholly without their points of 

 contact with certain vegetable organisms, but are on the whole more 

 closely linked to the animal kingdom, and in their highest representa- 

 tives the Infusoria are certainly of the nature of animals. 



The peculiarities of these three groups lie for the most part in 

 their modes of nutrition and motion, but many other differences exist 

 in their reproductive processes and general organization. The Ehizo- 

 poda, for example, with their naked mass of protoplasm, move by 

 means of rapidly changing lobose or filiform processes (so-called 

 " Pseudopodia "), which we have already seen in the Amoeba, one of 



1 In regard to the organisms of the small-pox lymph, see Cohn, Archiv f. pathol. AnaL, 

 Bd. lv., p. 229, 1872 ; and on those of diphtheria, fcce Oertel, Deutsch. Archiv f. Tclin. 

 Mcd., Bd. viii., p. 242, 1871; also Klebs, " Beitrage zur Kenntniss der pathogenen Schi- 

 zomyceten :" Prag, 1874. 



2 [For an account of the controversy regarding the comma Bacillus, see Klein, " Micro- 

 Organisms and Disease," Second Ed., London, 1885 ; also various papers in the Lancet and 

 liritish Medical Journal, 1884 and 1885 ; and, for a brief summary of the question, Nature, 

 vol. xxxi., p. 97, 1885, and Lankester, ibid., p. 168. W. E. H.] 



