LETTER OF TRANSMITTAL. 



Washington, D. C, April 21, 1S90. 



Sir: I have the honor to submit herewith a report upou the para- 

 sites of sheep, which has been prepared with much care and will prove 

 of permanent value to all owners of this class of our domesticated ani- 

 mals. The information heretofore attainable on this subject in the 

 United States has been fragmentary and in many cases unreliable, 

 although the parasitic diseases of sheep are among the most frequent 

 and seriou? maladies by which this species of animals are affected. 



it has been the aim in the preparation of this volume to make the 

 descriptions and the illustrations so plain that any one will be able to 

 identify the parasites which he may find in his flock, and yet the sub- 

 ject is in some of its aspects so technical that it could not be presented 

 entirely in popular language. The technical descriptions which it is 

 deemed necessary to insert have, however, been placed in small type, 

 and those not interested in the characters by which the species are 

 identified can omit such paragraphs. The symptoms and appearances 

 l)resented by diseased animals and the treatment of the diseases have 

 been«given at considerable length, and these will be read with interest 

 by all who desire information on this subject. The illustrations are a 

 prominent feature of the work, having been drawn and lithographed 

 -with the greatest care, and every attention given to make them accu- 

 rate in their most minute details. Nearly all of these are original and 

 were drawn from nature. 



The nodular disease of the intestines, together with its cause, is de- 

 scribed for the first time in these pages. This disease is common and 

 wide-spread, but its cause and nature were mysterious until they were 

 discovered through the investigations of this Bureau. We have here 

 once again a demonstration of the value of systematic, scientific in- 

 vestigation of the diseases of animals, for the results obtained by the 

 studyof this malady are among the most interesting contributions of 

 modern research. The facts obtained in the investigations of the frtaged 

 tape- worm and the hair lung-worm are also of more than ordinary in- 

 terest. 



The subject of parasites and parasitic diseases is one of great impor- 

 tance, and must become more prominent as the number of domesti- 

 cated animals in the country increases and the pastures become more 



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