1^54 Ammal Iiepo7i for 19\^ of Royal Veterinani College. 



what ai)pears to be the rule in this couiitiw, the Strungylus 

 contortus was the species mainly respDnsible for the losses 

 during the past yean 



The adult worms, male and female, inhabit the true 

 digestive stomach, and the eggs which are there laid by the 

 females are carried out with the stomach contents into the 

 intestine and are eventuallj' expelled with the faeces. From 

 the eggs are hatched out the young worms. These young 

 worms nourish themselves on the organic matters present in 

 the fseces or earth in which they have been hatched out, and in 

 order to fit them for life in the sheep's stomach they have 

 to undergo a further process of development, which is accom- 

 panied by a shedding of their original cuticle or skin. When 

 the worms have reached this stage they are incapable of further 

 development in the outer world, but when they find their 

 way into the stomach of a sheep they rapidly attain to sexual 

 maturity, the males and females copulate and the eggs laid 

 by the latter begin to be passed out with the faeces. Both 

 the eggs and the young worms when first hatched out are 

 liable to be killed by frost or drought ; but when the latter 

 have undergone the process of development mentioned above 

 they are much more resistent to vicissitudes of weather, and 

 may retain their vitality for long periods, awaiting an oppor- 

 tunity to be taken in by a sheep. 



The points in the life cycle of the worms which are of 

 chief importance for an understanding of the manner in which 

 they cause disease in sheep are the following : — 



(1) The worms do not multiply in the outer world, since 

 only those in the stomach are capable of reproduction. 



(2) Although reproduction takes places in the stomach this 

 does not directly increase the number of worms there present, 

 because the eggs have to leave the body of the sheep in order 

 to be hatched out. 



(8) The fffices of sheep infested with stomach worms are 

 not immediately dangerous for the sheejj. The excrement and 

 the land on which it has been voided only become dangerous 

 when the eggs have hatched out and the young worms have 

 undergone a process of development. 



(4) Warmth and abundant moisture are favourable, while 

 frost and drought are fatal, to the eggs and newly hatched 

 young worms. 



These facts not only explain the occurrence of outbreaks of 

 parasitic gastritis, but also suggest the means by which the 

 disease may be prevented. There cannot be any doubt that 

 the explosive serious character of the outbreaks during the 

 second quarter of 1911 were the outcome of the preceding 

 mild and wet winter and spring. The fact may be recalled 



