808 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
due to staining is not quite clear. The tissues were hardened in 
sublimate and alcohol and stained with hsematoxylin. 
Pfeiffer’s Parasitic and Pathogenic Protozoa.* — The second and 
much enlarged edition of Dr. L. Pfeiffer’s work on the Parasitic 
Protozoa is on similar lines to its predecessor. The illustrations and 
the letterpress leave much to be desired, the former being extremely 
archaic and the latter full of typographical blunders. Yet this is the 
only work which deals with the very interesting problems connected 
with the symbiosis of Protozoa and the cells of higher animals. Many 
of these Protozoa pass the whole of their existence within cells, and the 
nature of their parasitism therefore becomes extremely interesting. 
Does their presence necessarily imply a pathogenic influence eventually 
destructive of the host ? Are they merely harmless guests ? Or is their 
parasitism potentially noxious, that is, requiring some further deciding 
factor than their mere presence for the development of disease. 
In what way are they pathogenic ? What is the nature of their 
pathology ? Is it by their direct action on the infected tissues, the latter 
becoming so altered as to render them not only unfit for, but even noxious 
to the organism of their host, or is it from the absorption of the products 
of the metabolism of the parasites. All these questions and many 
others connected with the Protozoa remain to be answered, for very little 
is known about them, although during the past few years more attention 
has been devoted to the subject and the presence of parasitic Protozoa 
has been demonstrated for certain acute and chronic disorders in 
Mammals, Birds, and Eeptiles. 
But the author of the ‘ Parasitic Protozoa * is not content with a few 
sure and certain instances, he more than suspects that diseases such as 
herpes zoster, variola, vaccinia ovina, varicella, and perchance also 
scarlet fever, measles, molluscum contagiosum, and last but not least 
carcinoma are caused by intracellular parasitic Protozoa. 
Kruse, W. — Der gegenwartige Stand nnserer Kenntnisse von den parasitaren 
Protozoen. (The present condition of our knowledge of Parasitic Protozoa.) 
Hyg. Rundschau , 1892, pp. 357-80, 453-85. 
* ‘Die Protozoen als Krankheitserreger sowie der Zellen- und Zellenkern- 
Parasitismus derselben bei nicht bakteriellen Infectionskrankkeiten des Menschen,’ 
2nd edition, Jena, 1891. See Centralbl. f. Bakteriol. u. Parasitenk, xii. (1892) 
pp. 168-71. 
