466 LEFEBVRE. 



a priori. The invasion of a sebaceous gland by the larva or eggs of 

 Demodex being possible only by the orifice of the excretory duct, those 

 glands which are obstructed by comedones are protected from infection. 

 Any parasite found in them can only have penetrated there before the 

 formation of the plug. 



If parasites which have previously penetrated glands bearing com- 

 edones should generate larvae, the larva? can not spread until after the 

 expulsion of the comedone. Now, the latter arc known to persist some- 

 times for months; indeed, I have met with some that I could extract only 

 with the bistoury. Old comedones are often definitely encysted and the 

 gland ceases to perform its function. In short, comedones are not 

 habitually due to Demodex and they are unfavorable to the propagation 

 of this parasite. 



However, I did encounter Demodex on a leper who had severe acne 

 molluseum which had infected a great part of his face, but the sebaceous 

 glands taking part in this acne performed their functions abundantly 

 and on the slightest pressure their product escaped easily. 



I have been aide more precisely to lix the percentage of lepers having 

 Demodex than I have that of persons in health harboring this organism. 

 My observations have been made on a hundred lepers. I collected the 

 product of the sebaceous glands from all parts of the body, but more 

 especially from the sides of the nose and the ear. To judge from this 

 series, the average percentage of lepers harboring Demodex does not seem 

 to exceed 25. 



I must say that in this search for Demodex on lepers Borrel has been 

 move fortunate than I. lie says, "Among the lepers we examined, we 

 each time found Demodex in the follicles." 9 However, he does not men- 

 tion the number of patients he examined. His investigation was made on 

 the lepers in the Hospital Saint-Douis in Paris. 10 in so far at least as 

 regards the direct search for Demodex in the follicles. The examination 

 of mierotomic sections of tumors was made from leprous nodules of 

 the hose which he received from Algiers and Bergen. Borrel speaks only 

 of one of these nodules, of which he gives an excellent description, but he 

 does not say whether he found Demodex in the others, nor how many 

 tumors he received. Therefore it would be difficult to form a statistical 

 argument from his report "Sur les Acariens et la Lepre." His discussion 

 on the function of Acarina in Cancer is richer in material and, if one 

 may reason by analogy between two such different diseases as leprosy 

 and cancer, this comparison would afford some grounds for his hypothesis. 



If the results of my researches on the lepers of San Lazaro are accepted, 



"Acariens et Lepre. Ann. Just. Past. (100(»), 23, 127. 



10 When I had the opportunity of examining the lepers at the Hospital Saint- 

 Louis a few years ago, they were about fifteen in number. I do not know how 

 many there are at the present time, nor whether M. Borrel looked for Demodex in 

 all of them. 



