INDUSTRIAL PROGRESS DURING THE YEAR 1874. hii 



lution was not, showing that the color is fixed by the or- 

 ganic matter of the bones. 



Miiller has examined the respiration of frogs, and finds (l) 

 that the direction of a series of observations is constant; (2) 

 that the brown frog consumes more oxygen than the green 

 frog; (3) that they both consume less when hungry ; (4) that 

 they consume the same amount in the winter time when un- 

 der water ; (5) that on being released, after being frozen in ice 

 eight hours, they breathed at the normal rate. He also ob- 

 served that, weight for weight, a mouse consumed twenty- 

 four times as much oxygen as a frog. 



Forster has made a series of experiments on the impor- 

 tance of the inorganic constituents of food. He divides the 

 salts of the food into two classes: those which are firmly 

 combined with combustible substances, and are indispensa- 

 ble ingredients of the juices and blood; and those which are 

 simply dissolved in the juices. The latter greatly preponder- 

 ate, being either introduced from without or produced with- 

 in the body. The former class can not leave the organism 

 when in combination, nor even when dissolved in the juices. 

 Experiment shows that although the salts are to a great ex- 

 tent retained and used over, a certain amount is excreted. 

 Hence, when salts are withheld, the whole body, but especially 

 those parts actively changing, like blood and muscle, become 

 gradually poorer in salts and richer in albumin; but, though 

 the total quantity in the body is lessened, the mixture of 

 salts in the tissues and juices is unchanged. The diminution 

 of salts in the muscles causes muscular exhaustion ; and in 

 the nerves, first excitability, and then paralysis of the nerve- 

 centres. The quantity of salts necessary in food is less than 

 has hitherto been supposed. 



Heitzmann has shown that the administration of lactic 

 acid to cats and dogs, either by the stomach or hypodermic- 

 ally, causes, within two weeks, swelling of the epiphyses of 

 the long bones, catarrh, and other symptoms of rachitis ; a 

 result confirmed by microscopical examination of the bones. 

 Continued for four months, the bones soften, and appear like 

 those affected with the disease called mollities osseum. Ro- 

 dents do not seem to be affected by lactic acid, even after 

 eleven months. Since lactic acid is to be found in the urine 

 of rachitic patients, and Schmidt has found it in a long bone 



