1900] MICROSCOPICAL JOURNAL 203 



first experiments had been made with the blood of cattle 

 immediately after they had been brought from the South. 

 In the next experiment blood was used from an animal 

 that had been away from the infected district seventy- 

 four days. This also produced disease. In succeeding 

 years experiments were made by inoculating with the 

 blood of cattle that had been under observation, with no 

 chance for reinfection, for one year, two years, three years, 

 four years, five years, six years, and seven years, and in 

 every case the disease was produced. It was concluded, 

 therefore, that this contagion once introduced into the 

 blood of cattle remained there in an active condition 

 throughout the animal's life. 



We were now in a position to understand and explain 

 the principal features of this disease, that is, it was plain 

 that cattle in the infected district carried in their blood 

 the contagion of Texas fever ; that this contagion was in 

 reality a protozoan organism called the Pyrosoma higem- 

 inum, analogous to the parasite of human malaria ; that 

 this parasite was transferred to susceptible cattle outside 

 of the infected district by the Southern cattle tick, Boo- 

 philus bovis ; that Southern cattle, although carrying the 

 contagion, were harmless unless infested by this particu- 

 lar tick ; that the Southern cattle carried this contagion 

 in their blood for years after leaving the infected district, 

 and would again be dangerous to other cattle if by any 

 chance they were reinfested with the proper species of 

 ticks, A study of the biology of the tick showed that the 

 time required for the eggs to hatch depends upon the at- 

 mospheric temperature, and that all the mysteries of the 

 propagation and incubation of the disease depended upon 

 the hatching of thewe eggs. — Report Agr. Dept. 



Wanted. — Eiarth containg- diatoms from Redoado Beach 

 for a European subscriber who offers cash, or, in exchang-e, 

 Hungarian diatomaceous matcrialfrom St. Peter, C. W. S. 



