iS5 



different organs. In the sttidy of Pathology nothing 

 however in the shape of morbid material is wasted by 

 a worker ; Dr. Clarke therefore set himself to 

 investigate the epidemic so handy to his door. He 

 had previously noticed that all the first cases were 

 among the breeding birds and that these birds were 

 being supplied with egg food. He also noticed a fact 

 with which all observant breeders are well acquainted, 

 viz., that for the first two or three days of the young 

 birds' life the old ones either eat their excreta or at 

 least remove it in their beaks from the nest, passing 

 immediately to their alternative occupation of feeding 

 the young with the egg and other food. Now with 

 all the care in the world no one can guarantee that 

 never shall some minute morsel of egg become septic 

 in some corner of aviary or cage ; and so the birds 

 were fulfilling precisel}^ the same conditions as I have 

 before described as necessary for the production of 

 this fell disease. The bacilli, which exist everywhere, 

 infected the egg; the egg with its bacilli was 

 swallowed; while in the bird's intestines these 

 bacilli rapidly multiplied by their own method of 

 fission ; and consequently the new generations of 

 them, propagated as they were in the most favourable 

 environment, became progressively more and more 

 virulent. Add to these facts the additional one of 

 what ma}^ be called the " circular system " and the 

 picture is complete. 



It would thus seem that the production of an 

 epidemic, or at any rate of a few cases of infectious 

 septic disease is a simple matter. Not by any means 

 that egg is a " first cause" ; it is nothing of the sort, 

 but it zs a specially favouring agent (or second cause) 

 which often turns the balance between conquering or ' 

 being conquered on the part of the bird when 

 invaded, as it pretty constantly is, by the bacillus. This 

 latter is the true first cause, and it is quite sufficient 



