RESEARCHES ON ACARIDS AMONG LEPERS. 473 



to prove this would be difficult, but the preceding considerations render 

 this question unimportant. 



I have had no opportunity to study the migratory acarids cited above 

 from the point of view of leprous contagion, except Sarcoptes scabiei. 



This acarid is essentially migratory. The female alone forces its way 

 into subepidermic tunnels which she has burrowed for the purpose of 

 laying her eggs, and remains in this situation until she dies; the male 

 raises a small epidermic pellicle under which he hides, but this is only a 

 temporary shelter and he soon leaves it to form a similar one elsewhere, 

 and so on. The remainder of the life of these parasites is passed on the 

 surface of the skin. 17 Here, no a priori objection can be raised against 

 leprous contagion by the medium of the Sarcoptes of the itch. It is a 

 mere question of fact. 



I observed an epidemic of the itch among the lepers of San Lazaro and 

 learned from questioning them that the greater number of the lepers then 

 afflicted with the disease did not have it before entering the hospital as 

 leprous patients ; moreover, I saw the itch in an early stage on several of 

 the lepers. Finally, several of the lepers told me that they had never had 

 the itch previously. If their assertions can be trusted, I must at least 

 conclude that the Sarcoptes of the itch is not the normal agent of leprous 

 contagion. 



I have sometimes encountered the Hansen bacillus in the parts affected 

 by the itch, particularly when a leper, by scratching, has caused erosions 

 which suppurated; but as the erosions were in the immediate vicinity of 

 leprous ulcers, it is not proved that the bacilli had been imported by 

 the Sarcoptes. I have never found the Hansen bacillus in the itch 

 furrows formed in parts not previously leprous. On triturating bodies of 

 Sarcoptes for bacteriologic examination, I did not find the bacillus of 

 leprosy. 



Finallv, I treated and cured several cases of itch on lepers, and after 

 the disappearance of all signs of the infection, the healed parts after an 

 observation carried on for several months showed no symptoms of leprosy. 

 However, evidently no great importance can be attached to this last 

 statement, as we are entirely ignorant of the duration of the incubation 

 period of leprosy. 



From all this, only a negative conclusion can be reached, since we 

 have no conclusive proof that the Sarcoptes of the itch is the normal 

 agent of leprous contagion; but neither is there proof that it can not 

 transmit leprosy accidentally. 



There remain two other acarids which I have encountered among 

 lepers, but which, for want of sufficiently detailed literature, I can not 

 determine definitely. One is of a species of the genus Tyroglyphus, 

 the other of a species similar to this genus. 



17 Megnin, loc. cit. 219. 



