NINTH ANNUAL REPORT. 147 



Deformities of the skull have not been noted by us, although 

 the bones are found extensively softened and thickened. 



There is no question in our minds but that the degree of de- 

 formity is dependent mostly on the amount of weight or pressure 

 to which the individual bones are subjected, since, in the various 

 parts of the body, all of them are found to show the essential 

 pathological changes in about equal degree, though we believe 

 that they are inaugurated in the lower extremities and spinal 

 column. In the terminal condition any of the bones, even the 

 petrous portion of the temporal bone, may be readilv cut with 

 a scalpel without previous decalcification. 



As a rule, where secondary injury is not present, the diseased 

 bones present on their external surface very little indication of 

 disease and none of inflammatory reaction. Periostitis occurs, 

 we believe, only from some outside cause and generally the bone 

 is smooth, though the epyphyseal ends appear symmetrically swol- 

 len. The animals ordinarily evince little or no pain on pressure 

 of the bone, even to the point of crushing it, for in a large pro- 

 portion of cases the femurs, for instance, may readily be broken 

 with the fingers. One must remember in this respect, however, 

 that many of these animals do not appear to be very sensitive 

 to pain from any cause. 



The gross appearance of the sectioned bone varies greatly. 

 Generally the compact external plates are considerably thinned, 

 the marrow space being considerably increased. As a rule, the 

 outer shell presents a certain amount of lime salts and is still 

 more or less hard, but in some cases, particularly near the epyphy- 

 seal ends of the bone, it is found to be soft or semi-elastic, 

 resembling in its physical attributes cartilage more than bone. 

 The periostium shows no notable change in most cases. In the 

 cases of the large flat bones, the entire thickness is transformed 

 into an even greyish semi-cartilaginous material. 



The bone marrow also varies greatly in appearance ; in 

 places, usually in the shafts of the long bones, it is bright red 

 in color and presents semi-solid areas resembling nodules of 

 cartilage. In the epyphyseal ends, and sometimes throughout 

 the shaft as well, the medulla is represented by a difl^use soft 

 greyish mucoid material in which fine spicules of semi-cartila- 

 ginous bone are found representing the normal comjiact frame- 

 work of the marrow and cancellous portions. Where cartilage 

 and bone are closely united, as over the head of the femur or 

 between the vertebrae, the marrow seems to have extended into 

 and replaced the cartilage to a large extent. Occasioinl cystic 



