OSTEOPOROSIS. 265 



least 100 victims every year. Some parts of this island of tlie 

 Sandwich group are very damp, and have an annual rainfall of about 

 150 inches. Other districts are dry, and are rarely favoured with 

 rain. In the former, the disease is remarkably prevalent, but it 

 never occurs in the latter. Removal of affected animals to a 

 dry district is followed by immediate improvement and ultimate 

 recoA^ery, which is a termination that does not otherwise take place. 

 He states that horses will contract it under any conditions of diet, 

 and that it seems to be regulated only by climate. " Altitude and 

 temperature do not appear to affect the course of the disease. In 

 my district, cases are seen both at sea level and on elevated lands 

 where the thermometer occasionally registers freezing point. Owing 

 to the lack of nutritious forage there are no breeding establishments 

 in the rainy districts, and of the few foals which are born, nearly 

 all succumb to the disease before attaining maturity. The geo- 

 logical formation of the island is similar throughout its whole 

 extent, and is purely volcanic. . . The recoveries resulting 

 from change of locality contrast strongly with the inadequacy of 

 drugs. Two thorough-bred animals, each four years old, were in 

 the last stages of this disease; they were removed to a dry dis- 

 trict, well fed, and allowed the run of a small paddock. Restora- 

 tion to normal health was effected in three months." 



NATURE OF THE DISEASE.— Osteoporosis appears to be a specific 

 inflammation of bone by which a portion of the earthy matter become dis- 

 solved. Its course close] v resembles that of human "rarefying ostitis," 

 which is described as follows by Erichsen : " A portion of compact bone 

 undergoina: this change is in the earlifst stasfes slightly redder than natural; 

 the openings of the Haversian canals after a time become somewhat in- 

 creased in size, and consequently a larger number are visible to the naked 

 eye. As the process advances, the Haversian canals increase at the expense 

 of the bone surrounding them, and when they reach a sufficient size, they can 

 be seen to contain a small quantity of pink granulation tissue surrounding the 

 vessel. If a portion of the bone at this stage be macerated, it presents a 

 porous, spongy appearance, almost resembling cancellous tissue." Tlie 

 Haversian canals are the extremely minute canals (they vary from a 200th 

 to 2,500th part of an inch in diameter) which run through the substance of 

 bone ; and cancellous tissue is the spongy portion of bone. 



Considering that osteoporosis is, as far as I have been able to find out, 

 confined to certain districts, and that in other places errors of diet, no matter 

 how much intensified, appear to have no effect in setting up this disease ; I 

 cannot resist making the conjecture that it is due to some specific poison 

 contained in the fodder consumed. Up to the present, no exact information 

 has been obtained respecting the manner in which the diseased condition of 

 bone is brought about. The facts which I have given in the preceding para- 

 graphs of this section, show that osteoporosis can occur when the food has a 

 sufficiency of nutrient matter, including salts of lime. 



DISTINGUISHING SIGNS.— See "Distinguishing signs of rickets," 

 page 268. 



PRINCIPLES OF TREATMENT.— I have seen the best results obtained 

 from the adoption of the principle that the disease is due to some noxious 



