K. F. MEYER 617 



from 0.1 to I cc. of a broth culture (Smith,' Uchida,^ Freund,^) or surviv the injec- 

 tion and die three weeks later when subjected to low temperatures or other environ- 

 mental changes (Okamoto). In the experiments of Uchida neither the "culture" nor 

 the "body" strains caused infections when fed or applied to the conjunctival sac or 

 by inhalations. 



The clinical symptoms are variable and uncertain, although a watery nasal dis- 

 charge and an enlargement of the cervical lymph nodes has been observed by the 

 writer. Equally inconclusive are the autopsy findings although the frequencies of the 

 principal lesions are recorded as follows: serofibrinous, frequently hemorrhagic 

 pleurisy (Smith, Branch), acute lobar (Christiansen, Freund) or chronic unresolved 

 bronchopneumonia; infarct-like patches of lobular and lobar distribution in the 

 cephalic and caudal lobes with adhesions; enlargement of the spleen, purulent perito- 

 nitis with and without extensive inflammatory ulcerative involvement of the uterus 

 (Richters, Okamoto); hemorrhagic or seropurulent pericarditis; otitis media (Branch) 

 and occasionally subcutaneous phlegmonous processes. A bacteriological examina- 

 tion established the diagnosis and proved the septicemic character of the disease in 

 approximately 95 per cent of the cases studied by the writer. 



The epidemiology of spontaneous pneumococcus infections in guinea pigs deserves 

 considerable investigation. The reports of Freund and others indicate that the incit- 

 ing organism may be widely prevalent. At the end of an epidemic he found ig per 

 cent and during the endemic period approximately 27 per cent carriers with the 

 pneumococcus either in the nasal passages or in the tracheal lymph nodes. It is not 

 unlikely that the percentage would have been increased by an examination of the 

 sinuses and the middle ears as advocated by Branch. The writer has found that ap- 

 parently healthy animals of certain breeders may show a carrier percentage of as 

 high as 60 per cent provided the examinations for the pneumococcus are made at 

 autopsy. Animals with snuffles can readily distribute the organisms which are, how- 

 ever, of very low virulence. The portal of entry of these organisms is unknown. Some 

 workers suspect the upper respiratory tract (Freund, Branch); others, the uterine 

 cavity. One fact is certain — the exact reproduction of the spontaneous disease is 

 practically impossible. Proved contact infections are very rare although Freund 

 demonstrated the dissemination of pneumococci by exposing blood plates in the 

 animal room. Smith expressed the view that the various guinea pig epidemics re- 

 ported from different countries were due to pneumococci of widely different degrees 

 of virulence, but it is now generally believed that the epidemic outbreaks of a pneu- 

 mococcus or any other similar infection is controlled by the host susceptibility and 

 not by the virulence. From the various reports one must conclude that two or three 

 factors affect the susceptibility: pregnancy and parturition, sudden or prolonged 

 changes in the temperature of the environment, and perhaps dietary deficiencies. To 

 these the writer would like to add, from personal observation: crowding in dark and 

 dusty cages, superimposed infections (pasteurellosis), and various experimental pro- 

 cedures. The contributory conditions are probably in many ways similar to those 

 recently elucidated by Webster^ in his studies on snufiiles in rabbits (see p. 624). 



• Smith, T.: loc. cit. ^ Uchida, Y.: loc. cil. ^ Freund, R.: loc. cit. 



"I Webster, L. T.: /. Exper. Mef., 45, 911. 1927. 



