ETIOLOGY AND MODES OF PROPAGATION. 53 



influences, wliicli determine tlie appearance of the fever, we 

 know little. 



Wliile if proved to be contagious — capable of propaga- 

 tion from one animal to another — the exact nature of the 

 contagium has not in the present state of our knowledge 

 been determined. Whether it is to be regarded, as the views 

 of Hallier and others indicate, as consisting of the microscopic 

 spores of fungi or other low forms of vegetable life ; or as 

 minute, granular matter floating in the air, and derived from 

 living but diseased animal tissue, opinion is divided. 



The theory propounded by Dr. Beale, and one which in our 

 time has received a large amount of support, is that the con- 

 tagium of these specific diseases ought to be regarded as either 

 consisting of, or contained in, the nuclear or granular plasmic 

 material, of varying form, size, and structure, which, separated 

 from the living diseased animal, is capable, when gaining 

 access to the body of one susceptible, of growing and increasing 

 at the expense of the elements of that body, and of inducing 

 some form of specific disease. And that in cases of in- 

 creased body-temperature this living, germinal, or bioplasmic 

 material is capable of wondrous and rapid increase. 



Experimental research, however, seems to tell us that these 

 specific contagious diseases are more correctly regarded as 

 originating through the implantation in the healthy animal 

 of individual living organisms or their germs ; that these 

 living contagia have proceeded from previously living organ- 

 isms, and are proceeding to other and like living organisms. 

 Further, that it is probable that each specific disease owes 

 its existence to the presence and activity of a specific and 

 individually distmct living organism. 



Symptoms, Course, and Complications. 



To give a colour to this universal, convertible, and convenient 

 name ' influenza,' divisions and groupings of it have been 

 attempted, and their character indicated by such terms as 

 catarrhal influenza, typhoid pneumonia, typhoid pleuro- 

 pneumonia, rheumatic influenza, catarrho-rheumatic, etc. 

 Certainly we do in actual practice encounter various forms and 



