I02 Surgical Diseases and Surgery of the Dog 



times as large as normal. The lobes and isthmus in these cases were 

 so developed that they formed a single horseshoe-shaped body al- 

 most encircling the trachea. The swelling generally disappears later. 

 It is believed that heredity plays some part in its development, but 

 it is also witnessed in puppies whose parents possess thyroids show- 

 ing no deviation from the normal. 



In point of development even the normal gland may show 

 considerable variation in the newly-born animal, the difference de- 

 pending essentially upon the degree of development of the colloid- 

 containing vesicles. 



Very young dogs are often seen with enlargement of the gland. 

 It may commence soon after birth particularly in members of cer- 

 tain breeds, namely, Pomeranians, French Pointers, Dachshunde, 

 Spaniels, and lap-dogs. Greenhow saw it in India, and Bramley, 

 writing in 1833, found it to be quite common as a "lobulated bron- 

 chocele" among puppies one month old bred from English dogs 

 in the trans-Himalayan regions. It seldom becomes large when 

 arising in young dogs, but gradually becomes reduced in size, 

 though in some instances will recur periodically. 



Enlargements commonly occur during the course of general 

 diseases. In the experience of Zschokke it is a rare thing to find 

 dogs free of thyroid enlargements in some of the cantons of Switzer- 

 land. 



Several forms of Struma are recognized. The enlargement 

 may be the expression of extreme vascular engorgement (Hypere- 

 mic struma). This is of a transitory nature and with little if any- 

 pathologic significance. Muehlibach pointed out that it occurs dur- 

 ing the estrual period, and Bardeleben saw it in pregnant females.. 

 Pflug refers to a remarkable periodic recurrence in members of 

 certain breeds, particularly Blenheim Spaniels, the swelling appear- 

 ing coincident with even a slight cold, but disappearing within 

 two weeks. 



The commonest form is that of diffuse parenchymatous hyper-^ 

 plasia (Hyperplastic, Follicular struma) with or without a certain 

 amount of proliferation of the stroma and increase of gelatinous 

 contents in individual vesicles. 



When a hemorrhage occurs in one of the goitrous nodules^ 

 the extravasate undergoes an absorptive change, and according to 

 its age there may be anything from true bloody contents. 



