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very appropriate precedent, the Texas fever, a cattle disease the etiology 

 and propagtion of which were so ably cleared up, in 1892, by Dr. Theobald 

 Smith, chief of the Division of animal pathology in the Bureau of Animal 

 Industry, United States of America. Dr. Smith proved that the germ of 

 the disease is a blood parasite, and that it is propagated by the cattle tick. 

 The germs sucked in with the blood of diseased cattle reach the eggs of 

 the tick, and the new generation of ticks, developed from the infected eggs, 

 convey the Texas fever to the sound cattle upon which they are applied. 

 His experiments were repeated and confirmed in eastern Africa by Koch, 

 who, in view of the relations which seem to connect the presence of mosqui- 

 toes with the transmissibility of malaria, does not hesitate to make those 

 insects responsible for the propagation of the malaria infection. He does 

 not think, however, that the latter can be communicated by so simple a 

 process as that of a mosquito first stinging a malaria patient and afterwards 

 a sound person, such as I have, in my theory, considered capable of causing 

 the transmission of yellow fever. The grounds for this distinction, however, 

 are not very apparent. In the case of the tick, which is supposed not to 

 attack a second animal after parting from its first host, the exclusive trans- 

 mission by the second generation, infected through the eggs, may be cons- 

 idered a necessity; but it is otherwise with mosquitoes, at any rate, with 

 those which I have observed in Havana. After an interval of two or more 

 days, which they require to digest the blood and empty themselves, they 

 are ready to sting the next victim that offers, and may do so as many as 

 ten or twelve times, during the thirty or more days that I have been able 

 to keep them alive. It is, therefore, quite admissible that, when the mos- 

 quito becomes contaminated, not only its eggs but also its salivary and 

 venom glands may be invaded by the pathogenous germs, so that the latter 

 may be discharged with the secretion of those glands along the track of 

 the wound, and into the capillary vessel entered by the sting when the 

 insect attacks its next victim. Indeed, on some rare occasions I have seen 

 mosquitoes die within twenty four hours after they have stung a patient 

 with severe yellow fever, without assignable cause, for they still retained 

 some of the blood which they had sucked ; whence it might be surmised 

 that the yellow fever germ is pathogenic for the Havana mosquitoes, 

 though the infection seldom proves fatal for those insects. 



In August last, during my stay in the field hospitals on the hills near 

 Santiago, I witnessed a fact which, as far as it went, agreed with my theory 

 about yellow fever, inasmuch as there were neither mosquitoes, mosquito 

 eggs, nor larvae to be found in my encampments, and not a single case of 

 yellow fever occurred among the one hundred and fifty men who came 

 under my observation, notwithstanding the daily communications with the 

 city. It was otherwise, however, in regard to malaria, for this constituted 

 the prevalent cause of sickness in all those camps. It assumed various types ; 

 the quotidian or tertain intermittent, the remittent, irregular or subcon- 



