Pathogenesis, Anatomical Changes. 939 



probably of far greater influence. This diminution of the food 

 salts in general may perhaps be held responsible for the in- 

 creased cerebral irritability which is a prominent symptom in 

 certain cases. If an intoxication or infection is the cause of 

 the disease, the presumable toxins or infectious substances may 

 cause disturbances in metabolism. 



Anatomical Changes. The epiphyses of the long bones are 

 thickened, club-shaped, the diaphyses are shortened and also 

 thickened (Fig. 158). The bony tissue is porous and softer 



Fig. 158. Rachitis. Skeleton of a setter. 



than normal, sometimes so much so, that it can easily be cut 

 with the knife. Some bones show bends and even breaks (see 

 Symptoms). On the cut surface of the bone, which has been 

 cut lengthwise, there is visible, between the periosteum and 

 the bone tissue, a vascular, soft, spongy layer which in part 

 remains adherent to the bony substance when the periosteum 

 is peeled off. This osteoid' layer is especially thick at the 

 insertions of large tendons or muscles, and at these^ places 

 exostoses are frequently formed. The epiphyseal cartilage is 

 not separated from the 'diaphysis by a bluish-white or yellowish 

 double ])and of barelv a few millimeters width, but there de- 



