Gapes. 



153 



hatch in from seven to forty days according to their surround- 

 ings and temperature. The ova and the embryos get taken up 

 by the young birds off the ground, or in the water, and possibly 

 a recently ejected female worm full of 

 well -matured embryos may be, and 

 often is, picked up and eaten, and in 

 this way birds other than the young 

 pheasants may convey the disease to 

 the rearing fields. In the trachea of 

 a jackdaw sent to the Field thirty- 

 seven fully developed gape worms 

 were found, yet the bird, when killed, 

 was in apparently good health. 



The infection undoubtedly occurs 

 through ingestion. The exact manner 

 in which the embryo makes its way 

 from the oesophageal tract into the 

 respiratory tract has not yet been 

 definitely ascertained ; but on this 

 point there seems to be a general con- 

 sensus of opinion, namely, that the 

 embryo, whether swallowed as such or 

 hatched from the egg after the egg or 

 parent worm has been swallowed, finds 

 its way through the CESophagus or pro- 

 ventriculus into the lungs and so 

 into the trachea. Dr. Walker gives 

 instances of finding the embryo 

 in the oesophageal tissues ; M. Megnin 

 shows that the embryo can easily 

 teach the air-sacs and bronchi from 



the CBSophagus ; Euilliet alludes to the various effusions found 

 in the lungs of birds suffering from gapes ; and very many of 

 the birds examined at the Field that were suffering from gapes 

 presented similar pneumonic symptoms ; so that it seems 

 reasonably clear to conclude that the embryos, after being 



GAPE WORM {Syngamvs 

 trachealis) MAGNIFIED. 



