03S Rachitis. 



It also appears thinkable that, according to the degree 

 of lime deficiency and to the external influences, either the 

 proliferating process or then the osteoporosis is more pi'omi- 

 nent, the latter being indeed sometimes alone present (so-called 

 juvenile osteomalacia). It might be assumed that when the 

 affected animals are prevented from motion, or when the ani- 

 mals avoid all vigorous motions, because the bones are sensi- 

 tive in consequence of their lessened resistance, the process 

 of proliferation is far less intense than in animals in which 

 the mechanical influences can manifest themselves fully. It 

 need not be settled in this connection whether the proportions 

 of the other salts contained in the food have any influence. 



These considerations mav perhaps explain why some authors jirodiiced typical 

 rachitis by withdrawal of lime, while with similar methods of experimentation 

 others could only cause osteoporosis and marked proliferation of the epiphyseal 

 cartilage, and still others only osteoporotic changes. 



If the rachitis is based upon an intoxication or infection, 

 an inflammatory process in the bone tissue will probably be 

 primary and in such a case the bone salts may be dissolved 

 and absorbed, causing the bones to lose their firmness. In 

 the further course, however, similar reparatory processes would 

 occur in the bones as take place in lime deficiency under the 

 stimulation of the mechanical influences mentioned. 



The process which takes place in the bones causes in tliem 

 various changes in form. These are partly due to the prolifera- 

 tion in the bones and are therefore developed especially in 

 those portions of the body in which the bones are more exposed 

 to mechanical influences, during motion or during the chewing 

 of hard food-stuffs, or in rooting; this is true especially for 

 the epiphyses of the long bones, the maxillary or face bones, 

 also for tiie ribs which are in constant motion during respira- 

 tion. These external influences, which differ according to 

 species and breed and according to the care of the animals, 

 may produce the most varied combinations and forms in the 

 bony changes, and especially in pigs tlie maxillary or face bones 

 are often strikingly altered. The diminished firmness of the 

 bones leads on the one hand to curvatures, under the weight 

 of the body or from muscular traction, and on the other to 

 fractures. 



The diminished firmness of the bones is further responsible 

 for dragging upon the sensitive nerves in the periosteum and 

 in the bony tissue which in their turn cause pain in the bones 

 on motion. The proliferating osteoid tissue may even compress 

 certain nerve trunks (e. g., the nervus infraorbitalis [Hintze]). 



A high degree of lime deficiency in the organism may of 

 itself cause disturbances in metabolism because the calcium 

 is necessary for the binding of certain metabolic products. In 

 this respect, however, a diminution of the other food salts which 

 is often coexistent ■^^ith lime deficiency in the organism is 



