CHAPTER XIII 



applications of bacteriology 



Diagnostic Methods. 



Direct diagnostic methods — Direct diagnosis of the microbe — Cultures 

 from the blood— Examination of fseces — Indirect diagnostic methods 

 — Cytodiagnoses. 



Biological diagnostic methods — Agglutination : specificity and group 

 agglutinations : variations in bacteria from the agglutination point of 

 view — Prccipitatioji : employment in forensic medicine and in the 

 adulteration of foods— Applications to anthropology : confirmation of 

 the simian origin of man — ComplenUnt-fixation : first experiment of 

 Bordet : clinical application — Wassermann's reaction and the sero- 

 di^nosis of syphilis — The nature of the substances coming into play 

 in this reaction — Supersensitive reactions : tuberculin. 



The simplest and surest way to diagnose an infectious 

 disease is to demonstrate the presence of the specific microbe, 

 i.e., direct bacteriological diagnosis. When this is impossible, 

 indirect diagnosis is resorted to, i.e., the lesions of the tissues 

 which are constant accompaniments of a virus which is 

 invisible are sought for. The presence in exudates of certain 

 cell elements is noted, or the body-fluids and bacteria are 

 made to react together specifically (antibodies and antigens) : 

 in the latter case it is more properly a case of biological 

 diagnosis. 



Direct Diagnostic Methods. 



The microbe is sought for wherever there is a possibility 

 of finding it ; blood, exudates and transudates, pus, mucous 

 discharges, false membranes, ulcers and chancres, sputum, 



