" GROUSE DISEASE "—STRONGYLOSIS 



219 



Fig. 16. 



Morulce of eggs. 



invisible to the naked eye. They live in the caecal portions only of the 

 intestine of the Grouse. The sexually mature females give rise to 



•' ° Develop- 



their progeny as eggs, which undergo a certain degree of develop- ment 

 ment while still within the body of the worm. By the time they are body of the 

 laid the egg content has become subdivided into a large number of cells, 

 forming what is technically known as the morula (Fig. 16). As morulce these 

 eggs pass into and mix with the contents of the cajca, 

 all further development thereupon ceasing. This suspen- 

 sion of development appears to depend upon a lack of some 

 necessary stimulant in the ceecal 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 cseca 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 csecal contents had passed into the rectum, 

 and had there become diluted somewhat by the fluid from the 

 great 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 consequence, the parasites within the body 

 cannot increase in number by sexual multiplication. Each and every parasite 

 found within the body of the Grouse must therefore have actually entered 

 it from the outside. We shall see later that this explains the apparent 

 anomaly that whereas practically all Grouse are infected with Trichostrongi/lus 

 only some suffer from the disease. The egg, when newly passed, measures 

 0"075 mm. by 0"046 mm. and contains a morula composed of about sixty-four 

 cells. 



If a freshly passed csecal dropping be isolated and kept uncontaminated 

 no further development will take place in the ova contained in it. A fundus 

 will gradually grow upon it, and owing to this and bacterial con- oeveio 

 tamination the eggs eventually die. If the dropping be exposed ™^"* °f *^® 

 to the drying influence of sun and wind, as on the moors during ^^^ ^'^^y- 

 summer, it becomes caked and dry, and the eggs die. If, on the other hand, 

 csecal dropping be spread out in such a w^ay as to admit of the whole becoming 



