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Some IRecent Developmente of tbe Doctrine 

 of a Contaglum IDivum,* 



By R. Shingleton-Smith, M.D. Lond., B.Sc, F.R.C.P., 

 Hon. Fellow of King's Coll.., Lo7idon. 



Plate II. 



THE existence of a specific virus as the cause of various 

 contagious diseases has long been accepted as a fact ; the 

 influence of such a virus upon living bodies we call 

 I?ifection., and the respective diseases receive the name of Infectious 

 Diseases. 



The transmission of disease, whether immediate or mediate, 

 constitutes contagion—/.^., the communication of disease from one 

 person to another, either by contact, or through some medium 

 (air, water, etc.). The term contagion is usually applied to the 

 property of transmission, whilst the term contagium is applied to 

 the virus itself. The term i7tfectiofi is therefore a synonym with 

 contagion : both terms relate to specific diseases, always the same, 

 except in degrees of virulence, and communicated by varying 

 degrees of contact, mediate or immediate. 



The Zymotic or Enthetic diseases (svTiQrjfxi, I put in) are a 

 large class produced by inoculation or implantation from without, 

 and never arising spontaneously. The infecting agent has not 

 certainly been known, and various theories have been brought for- 

 ward concerning the nature of the poisons ; of these, the so-called 

 parasitic theory has found almost universal acceptance, and the 

 doctrine of a contagium animatum has been regarded as assured, 

 even although the actual contagium could not be microscopically 

 demonstrated. 



The observed laws of the contagious process have taught 

 much as to the nature of contagion in general, and have shown 

 that the phenomena of the dissemination of the contagium 

 correspond to growth, as of some living thing. 



" The various specific matters which effect contagion in the 

 living body, the respective contagia of the given diseases, seem 



'^ Read at a meeting of the Bristol Microscopical Society Nov. 14, 1889. 



