MALIGNANT DISEASE 



679 



tissue (Fig. 65, b). Save for the presence of these structures, 

 there is no proof that protozoa are present in, or are the cause of, 

 carcinoma. 



Another hypothesis of the nature of malignant disease js that 

 it is due to a blastomycetic infection (see p. 559) or that it is 

 caused by a myxomycete. 



Malignant disease occurs in all classes of vertebrates, and is 

 generally inoculable on an animal of the same species as that 

 from which it is derived, but not on other animals. The car- 

 cinoma of mice has been the subject of much investigation of late. 

 In the writer's opinion, the trend of recent research is to show 



FIG. 65. a, Buffer's or Plimmer's body in a cancer-cell ; b, the 

 archoplastic vesicle in spermatid of mouse. (After Farmer, 

 Moore, and Walker.) 



that malignant disease is not due to a micro -parasite, but is 

 derived from the irresponsible division of cells of the normal or 

 of embryonic tissues. 1 If there be a parasite, in all probability it 

 is intra-cellular, like the organism of plant cancer (Bacterium 

 tumefaciens) described by Erwin Smith. 2 



The molluscum bodies have likewise been regarded as parasitic 

 (coccidial) in nature, but with them also inoculation and cultiva- 

 tion experiments have failed. The virus is stated to be a filter 

 passer, as is also the case with bird molluscum. 



Certain malignant-like tumours of birds are also filter-passers, 

 e.g. chicken sarcoma. 



1 For further information consult Pathology, General and Special, ed. 4, 

 R. T. Hewlett (Churchill, 1917). 



2 Trans. XVIIth Internal. Cong. Med. Lond., 1913, Sect, iii, pt. ii, p. 281. 



