THE president's ADDRESS. 349 



some bacteria and spirochaetes, and above all the organisms known 

 as Chlamydozoa. I must at this point say a few words about 

 these Chlamydozoa, since they have been discovered or invented 

 very recently so recently that their very existence is not yet 

 beyond a doubt, and they are not as yet very familiar even to 

 the scientific public. 



An acquaintance with the Chlamydozoa has gradually been 

 forced upon scientific and medical investigators on account of the 

 connection which some species of these organisms have with certain 

 very well-known diseases of men and animals diseases of which 

 the true nature and cause have long been very problematical. 

 Such, in the first place, are small-pox and vaccinia, trachoma and 

 molluscum contagiosum in human beings, and in birds, epithelioma 

 contagiosum and diphtheria. Other diseases possibly attributable 

 to Chlamydozoa are hydrophobia, scarlet fever, measles, foot-and- 

 mouth disease of animals, possibly also distemper, and the silk- 

 worm disease known in Germany as " Gelbsucht." In all these 

 cases the specific virus, different in its properties in each instance, 

 has certain common peculiarities ; the pathogenic organism, what- 

 ever it may be, is a '' filter-passer " that is to say, it can pass 

 through ordinary bacterial filters without losing its virulence, 

 and it produces characteristic reaction-products or cell-inclusions 

 in the cells of the tissues which it attacks. 



As an example of a chlamydozoal organism, I may describe 

 briefly the life-history of the small-pox organism as it is stated by 

 Hartmann, Prowazek and others to take place.* The infection 

 begins with numerous "elementary corpuscles," minute grains 

 barely visible, which can pass through the bacterial filters, and 

 which occur both between and within the cells of the body. 

 Within the cells the elementary corpuscles grow slightly larger, 

 becoming the so-called "initial bodies." Their presence within 

 the infected cell stimulates an abnormal growth of the cell- 

 nucleus, which throws out nucleolar substance into the cytoplasm 

 of the cell. The parasites become enclosed in this nucleolar sub- 

 stance as in an envelope or mantle, hence the name Chlamydozoa. 

 The mantle with the contained parasites forms a characteristic 



* See especially Hartmann, Centralhl. Bakt. Parasitenkunde (T. Abt., 

 Ref.) xlvii., Beiheft, p. 94; Prowazek, Handhuch der Paihogenen Protozoen 

 II. (Leipzig, J, A. Earth, 1911); Prowazek & Aragao, " Variola- Untersuch- 

 ungen," Mem. Inst. Osicaldo Cruz I. pp. 147-158, pis. vii., viii., 2 text-figs. 



