98 RECREATIONS OF A NATURALIST 



infestation of the birds by a thread worm (or 

 nematoid) Strongylus pergracilis — while tape- worms 

 were also credited with helping a fatal result. But 

 the parasitic theory is disposed of on the simple 

 ground that hardly a Grouse is found to be free 

 from worms in its digestive system, and healthy 

 birds are found to possess both forms of worms 

 independently of any symptoms of Grouse disease. 

 The late Mr John Colquhoun, author of The Moor 

 and the Loch, as well as Dr D. G. Macdonald, who 

 has written a volume on the subject, regarded the 

 weakening of the bird's constitution by such causes 

 as bad seasons, insufficient food, and overstocking 

 as the prime factors in inducing the ailment, but 

 such opinions, while deserving of consideration, 

 leave the idea of a specific cause undiscussed. 

 Both Dr Farquharson and Dr Andrew Wilson have 

 expressed their belief that Grouse disease is an 

 epidemic and infectious fever, characterised by 

 inflammatory symptoms of the respiratory and 

 digestive organs. Dr Klein, recognising its in- 

 fectious nature, is convinced that it is due to the 

 multiplication in the body of the bird of a specific 

 germ, whose conveyance from the sick to the 

 healthy Grouse accounts for the spread of the 

 disease. The chief changes he finds in the 

 lungs, while congestion of the liver is also a con- 

 spicuous sign. In 1887 he went to Scotland at the 

 request of the Editor of The Field, for the express 

 purpose of investigating the cause of Grouse 

 disease. By making cultures from the blood of 

 Grouse which had succumbed to the disease, he 



