900 MICROBIOLOGY OF DISEASES OF MAN AND DOMESTIC ANIMALS 



High enemata of mild antiseptics have been used in the treatment 

 of this infection. 



PARASITES OF UNCERTAIN POSITION 



In Panama, there is a disease of man, somewhat resembling one 

 form of tubferculosis, which is caused by a parasite called Histoplasma 

 capsulatum. The only known stage of this parasite greatly resembles 

 the non-motile form of Leishmania donovani; but it contains only one, 

 not two masses of chromatin. This organism was at first thought to 

 be protozoon but is now considered to be a fungus. 



The name Toxoplasma has been given to a group of organisms which 

 usually inhabit the white blood cells of vertebrates. They do no 

 produce pigment. They have been found in animals and birds of sev- 

 eral species in many parts of the world. No parasite of this genus 

 has been found in man. 



CHLAMYDOZOA (Prowazek, 1907) 



This name is given to certain bodies because their presence excites the cell 

 containing them to produce a substance which surrounds them like a cloak. The 

 exact nature of these bodies is disputed; it is even doubtful whether they are para- 

 sites, or whether they are merely the expression of some morbid change, produced 

 in the cells, by an unseen virus which causes the disease. They have been found 

 in trachoma, a disease of the eyelids of man, in hydrophobia, in Molluscum 

 contagiosum, a skin disease, in smallpox, in vaccinia, and in scarlet fever. They 

 are mentioned with the protozoa because, if they are parasites, they are probably 

 more nearly allied to the protozoa than to the bacteria. They are extremely small 

 bodies, some measuring only 0.25/1 in diameter. They are spherical and occur within 

 the cells. In preparations stained by Romanowsky's method they are colored like 

 chromatin. 



RICKETTSIA (Rocha-Lima) 



Rickettsia is the name generally applied to a group of pleomorphic organisms 

 which are associated with typus, Rocky Mountain fever and trench fever. These 

 organisms vary in form from cocci to long threads of bacilliform organisms. They 

 stain with difficulty and have not been cultivated. They are transmitted by 

 insects. The organisms of trench fever and typus are carried by lice; that of 

 Rocky Mountain fever is carried by a tick. (Wolbach, 1919, proved that the 

 organisms causing Rocky Mountain Spotted Fever, which he calls Dermacen- 

 Iroxenus rickettsi, is carried by Dermacentor venustiis. 



ULTRAMICROSCOPIC VIRUSES (See page 119) 

 SPIROCH^TA (Ehrenberg, 1833) 



Many spirochaetes are, apparently, harmless parasites in shell fish, in the ali- 

 mentary canals of various animals and in the blood of fish, birds, and many mammals; 

 other spirochaetes produce disease in men and in lower animals. 



