62 Infection 



adhere to it. Of these, we can differentiate between forms 

 whose presence is unexpected and temporary ; others whose 

 presence may be expected ; and still others whose presence 

 is invariable. 



Elaborate investigations upon the bacterial flora of the 

 skin have been made by Unna*; Mittman,f who studied the 

 finger-nails, under which he found no less than seventy- 

 eight different species ; Maggiora, { who isolated twenty-nine 

 forms from the skin of the foot ; and Preindelsberger, who 

 found eighty species of bacteria on the hands. Undoubtedly 

 many of these organisms were accidentally present, and were 

 at least only semi-parasitic. Not a few were met but once 

 and were in no sense bacteria of the skin. The skin may 

 also be temporarily contaminated with bacteria from other 

 portions of the patient's body, as, for instance, from his 

 intestine ; thus Winslow || has found the colon bacillus upon 

 the hands of ten out of one hundred and eleven persons 

 examined. Wigura** also examined the hands of forty 

 persons in hospitals, finding tubercle bacilli in two out of 

 ten persons from phthisical wards in hospitals, colon bacilli 

 six times and typhoid bacilli once on the hands of nine 

 attendants in the typhoid wards. He found streptococci 

 and staphylococci many times. Welchff and Robb and 

 GhriskeyJ J seem to have been the first to make a clear dif- 

 ferentiation between the accidentally present bacteria and 

 the permanently parasitic organisms of the skin, and to show 

 that certain cocci, producing white and yellow colonies upon 

 agar-agar, were invariable in occurrence and penetrated to 

 the lowest epidermal layers. 



These cocci, of which Welch describes the most common 



* " Monatshef te fur prakt. Dermatol.," vii, 1888, p. 817 ;vm, 1889, 

 pp. 293, 562; ix, 1889, p. 49; x, 1890, p. 485; xi, 1890, p. 471; xii, 

 1891, p. 249. 



f'Archiv. f. path. Anat. u. Phys. u. f. klin. Med.," cxm, 1888, p. 

 203. 



J"Giornale della R. Societa d'Igiena," 1889, Fasc. 5, p. 335. 



"Samml. Medic. Schriften," herausg. von der "Wiener klin. Woch- 

 enschrift," xxn, Wien, 1891; "Rev. Jahresbericht iiber die Fort- 

 schritten in der Lehre von den pathogenen Mikroorganismen," vii, 

 1891, p. 619. 



|| " Jour. Med. Research," vol. x, p. 463. 

 ** " Wratsch," 1895, No. 14. 



ft "Transactions of the Congress of American Physicians and Sur- 

 geons," n, 1891, p. 1. 



tJ " Bulletin of the Johns Hopkins Hospital," in, 1892, p. 37, 



