TEXT-BOOK OP BACTERIOLOGY. 299 



and are colored quickly and intensely in cover-g-lass preparations 

 by the -watery anilin colors, for instance, fuchsin. 



The spirilla being found in all cases of relapsing fever and in these 

 only, it may be taken for granted that thej' are the actual cause of 

 the disease. This becomes still more probable by the fact that 

 previously healthy persons can be infected by transmitting blood 

 containing spirilla and a tj'pical relapsing fever produced in them (as 

 ascertained by Miinch and Moczutkowsky). Monkeys have also 

 been successfully inoculated by Koch and Carter, the animals being 

 after some time violently affected by fever, and their blood exhibit- 

 ing at the height of the fever large quantities of characteristic 

 micro-organisms. 



Efforts to cultivate these bacteria outside of the body, and thus 

 to obtain a view of their peculiarities and manifestations of life, 

 have thus far failed. 



We must, therefore, still decline to answer the question as to the 

 manner in which the spirilla invade our organism and give rise to 

 disturbances. It appears certain (from the experiences in the course 

 of various epidemics) that relapsing fever is a contagious disease, 

 directly transmissible from man to man. 



It is a striking fact that the spirilla are met with only during 

 the paroxysms of fever (occurring so peculiarlj' in this disease) 

 and disappear in the intervals. This process takes place (according 

 to Metschnikoff's investigations) in the folio wing way: at the height 

 of the attack the spirilla are found exclusively in the blood, but 

 not in the internal organs; during the period of the ante-par- 

 oxysmal rise of temperature, they gradually leave the circulation 

 and gather in the spleen, within which they die and are absorbed 

 by leucocytes. They are seen lying there densely rolled up, in heaps 

 or singly. 



Some individuals that did not perish and were preserved be- 

 tween the tissue elements become a nucleus for a new generation, 

 advancing into the blood after some time and giving rise to the 

 next attack. 



The spirilla are absent ^n the secretions of the body, such as 

 sweat, saliva, urine, etc. In a suspended drop of blood one sees the 

 narrow, delicate threads shooting through the field in rapid rota- 

 tions between the blood- corpuscles and pushing them in all direc- 

 lions; they appear singly, but frequently form groups by becoming 

 wrapped into dense, closely-encircled heaps. Their number does not 

 seem proportionate to 'the severity of the attack of the disease; 

 several fields must sometimes be searched before we see a single 

 one, while at other times they fill the blood in masses. 



