236 THE GROUSE IN HEALTH AND IN DISEASE 



cold has been tested by subjecting the metamorphosed larvae 

 to freezing in the cold storage rooms at the Albert Dock for a 

 period of a week. On being thawed out of the solid block of 

 ice they were found quickly to regain their activity. Exposure 

 to slow drying, on the other hand, under experimental con- 

 ditions, results in the death of the encysted larvae. Death from 

 lack of moisture must be continually taking place on the moors, 

 although there may often be, even at the hottest parts of the 

 day, an insensible transpiration from the growing plant, sufficient 

 to maintain the life of the larvae by preventing desiccation. 

 Burning and cutting appear to be the only practical means by 

 which infected heather plants can be properly purged. 



To any one unaccustomed to the moors it is a matter 

 of astonishment to notice what might be described as the 

 extraordinary insanitary condition of the Grouse's home. Nearly 

 every square yard of moorland shows traces of faecal deposits, 

 and this fact when once appreciated forcibly directs attention to 

 the unnatural over-population of the moors. 



When one remembers that practically all Grouse are infected 

 with Trichostrongylus pergracilis, and that from every dropping 

 thousands of potential parasites normally emerge, it becomes 

 evident that the greater the number of birds upon a given area 

 the greater in turn must be the infecting capacity of the moor. 

 But on most moors only a very small proportion of the heather 

 is suitable for food for Grouse at certain times of the year, 1 

 and as the Grouse is a very heavy feeder it follows that the parts 

 of the moor from which the food supply is derived are just 

 those likely to be the most heavily contaminated with droppings. 

 The number of birds on a moor should be correlated, not with 

 the size of the moor but with the extent of the suitable food 

 area thereon. The amount of stock on a large moor may seem 

 low proportionately to the whole area, but when estimated 

 in proportion to the food area it may prove exceptionally high, 

 and this means a high potential capacity for the production 

 of Strongylosis, whilst the entrance of a few bacteria or 



1 ride chap. xii. pp. 351 et seq. 



