BUREAU OP ANIMAL INDUSTRY. 135 



a study has been made of various methods of pasturing sheep with 

 reference to their effects upon stomach worm infestation. The results 

 are not yet available. 



INVESTIGATIONS OF PARASITIC PROTOZOA. 



In a study of the life history of Sarcosporidia it has been found 

 that the so-called spores penetrate into the intestinal cells and there 

 develop into male and female elements within a few hours. This 

 is the most important advance which has been made in elucidating 

 the life history of these forms since the discovery that animals could 

 be infested by feeding meat containing the spores of the parasites. 



INDEX-CATALOGUE AND COLLECTION OF PARASITES. 



The index-catalogue to the literature of medical and veterinary 

 zoology has continued to grow and now contains twice as many ref- 

 erences as when its publication was commenced in 1902. As a means 

 of keeping track of the immense amount of information which has 

 been collected by numerous workers all over the world, and which 

 is constantly being added to, it is of the highest value and enables 

 one to get together in a short time practically everything that has 

 been published upon any phase of the subject of parasitology. 



The collection of parasites maintained by the division for reference 

 purposes has been added to during the year, specimens having been 

 received from various sources both in this country and abroad. 



DIPS TO DESTROY TICKS, ETC. 



The outbreak of foot-and-mouth disease interfered so seriously 

 with the investigations of the use of dips in the treatment of live 

 stock for cattle ticks, mange mites, and other external parasites that 

 very little was done during the year. The work was resumed 

 June 1. 



One series of experiments was carried out in cooperation with tlie 

 Field Inspection and Biochemic Divisions. The results indicated 

 that arsenical dips containing unoxidized arsenic (sodium arsenite) 

 equivalent to about 0.2 per cent arsenic trioxid might contain in 

 addition sufficient oxidized arsenic (sodium arsenate) to give a total 

 arsenic content equivalent to about 0.6 per cent arsenic trioxid w^ith- 

 out injuriously affecting cattle dipped in the splution. If these results 

 are confirmed, it will be demonstrated that in testing arsenical baths 

 used for eradicating ticks only the content of unoxidized arsenic need 

 be considered, as a rule. In other words, if the field test shows that 

 the percentage of unoxidized arsenic in the bath is below standard, 

 sufficient arsenic may be added to restore the strength without fear 

 that the total percentage of arsenic will be raised so high that injury 

 to the cattle will result. 



A series of investigations on the treatment of sheep to destroy 

 sheep ticks was carried out under cooperation between the Salt Lake 

 City field station of the bureau and the Utah board of sheep com- 

 missioners. Dips containing cresylic acid were found to be effective, 

 but decision on the question of the most suitable remedies for sheep 

 ticks is reserved pending investigations now in progress. 



