DISEASES OF POUIvTRY. 195 



the roosting places become infected, and the contagion 

 is spread about the premises and it is not long before 

 other birds become diseased. Rivolta concluded that 

 the disease was not transmitted by placing the infec- 

 tious matter upon the sound skin; but Pfeiffer sue - 

 ceeded in causing the disease in fowls and pigeons by 

 inoculating it through punctures of the skin. San- 

 felice has repeated these experiments with the result 

 that the disease was invariably caused in pigeons by 

 inoculation into the eyelids ; and in the case of ten 

 pigeons with which the infectious matter was simply 

 smeared upon the eyelids, two contracted the disease. 

 It appears, therefore, that while an abrasion of the 

 surface or a deeper wound facilitates the entrance of 

 the contagion into the tissues, the parasite may in 

 certain cases, at least, penetrate the normal skin. 



Some have supposed that the bites of fleas and 

 mosquitoes, others that the punctures of ticks produce 

 this disease. Undoubtedly these act simply by fur- 

 nishing an easy entrance for the germs. The blas- 

 tomycetes or fungi appear to multiply outside of the 

 birds' bodies, probably in the accumulations of excre- 

 ment which exist in many poultry -houses. Some 

 moisture is necessary for the growth of these germs, 

 and hence it is not surprising that poultry raisers 

 have observed that the disease appears in those houses 

 which have leaky roofs or into which water can pene - 

 trate through the walls and thus moisten the drop - 

 pings. It is well known that fungi are most numerous 

 in the atmosphere during wet weather while bacteria 

 are most numerous during dry times. This fact may 

 account for the prevalence of sore head during wet 

 weather. It is, also, a matter of observation that this 

 disease is much more prevalent and fatal among late- 



