222 THE GROUSE IN HEALTH AND IN DISEASE 



parasite with a view to determining the manner in which it 

 is reproduced and disseminated, the mode of infection of healthy 

 birds and, if possible, to obtain experimentally the symptoms 

 of " Grouse Disease " under artificial conditions. In order also 

 to have some reasonable basis of fact upon which to establish 

 preventive and curative measures, a knowledge of the conditions 

 favourable to and inimical to the growth of the parasite at its 

 various stages of development became necessary. 



The sexually mature females give rise to their progeny as 

 eggs, which undergo a certain degree of development while 

 still within the body of the worm. By 

 the time they are laid the egg content has 

 become subdivided into a large number of 

 cells, forming what is technically known as 

 the morula (Fig. 20). As morulce these eggs 

 pass into and mix with the contents of the 

 caeca of the Grouse, all further develop- 

 ment thereupon ceasing. This suspension 

 of development appears to depend upon a 

 lack of some necessary stimulant in the 

 csecal contents, for the eggs may be found 

 alive and at the same stage not only several 

 days, but even so long as a month after 

 the death of the bird. In nature the caeca are evacuated 

 periodically, and the ova thus pass out of the body with the 

 soft portion of the bird's dropping. In one or two cases where 

 a portion of the caecal contents had passed into the rectum, and 

 had there become diluted somewhat by the fluid from the 

 large intestine, eggs were found to have progressed to the 

 formation of an embryo while within the body of a dead bird ; 

 but such a condition is obviously abnormal, and does not 

 invalidate the general conclusion that the eggs of this 

 parasite require to pass out of the body of the bird before 

 they are able to continue their growth, and that, in con- 

 sequence, the parasites within the body cannot increase in 

 number by sexual multiplication. Each and every parasite 



FIG. 20. 

 Morula stage of egg. 



