216 THE GROUSE IN HEALTH AND IN DISEASE 



the bird may rid itself of an excessive number of Tricho- 

 strongylus. This supposed recovery from Strongylosis may 

 have resulted from some unknown vermifuge herb or from 

 improved conditions of life. The worms, one must suppose, 

 remain in the gut ; but the congestion is overcome, and the 

 bird is not very much the worse for their presence. But, if 

 the congestion is allowed to continue and become chronic, the 

 digestion and absorption of food must go from bad to worse, 

 and with it every other function of the body. Nothing will 

 prevent the bird in this case from losing weight, and eventually 

 its life. 



As for the exact cause of the congestion, it may be due to 

 mechanical constriction of the filaments of the villi by the 

 nematode worms. Each time the gut contracts peristaltically 

 the worms have to hold on tightly to the gut lining to avoid 

 being dislodged with the dejecta, and the result is seen in sections 

 where the villi are evidently mixed up inextricably with the coils 

 of Trichostrongylus. Or the congestion may be due to the 

 chemical irritation of some poison produced in the gut by the 

 worms, or by the defective digestion of food stuffs, or by 

 bacteria living in the gut in its unwholesome state. Alter- 

 natively it may be due to some or all of these conditions 

 together. 



On the whole the mechanical view seems the most probable. 

 The peristalsis is acting in a way to dislodge the worm, and the 

 Trichostrongylus has no other way of retaining its position 

 in the caeca save by coiling round something, and the peristaltic 

 action of the caecum must be fairly strong in comparison with 

 the strength of the worm, for the free end of the worm has to 

 be released at every wave of peristalsis from immersion in a 

 thick, pasty material which is being driven outwards at each 

 contraction of the gut. It thus seems evident that the small 

 and delicate processes of the villi may be continually on the 

 stretch, at first looped round tightly by a worm, the coil may then 

 relax, blood may enter the capillaries, only to be compressed 

 anew and so on, conditions which cannot but produce irritation 



