JOLY 1, 1904.] 



SCIENCE. 



dioxide. In this oxidation just as many 

 heat units are liberated as would be set 

 free by the same kind of combustion in a 

 calorimeter. If work is done at the ex- 

 pense of the consumed food stuffs it has 

 been found that the animal makes a some- 

 what greater return of mechanical energy 

 than is possible with the best machines 

 known. But while all this is interesting 

 and important, it leaves the main question 

 still unanswered: How is it accomplished? 

 To effect such oxidations artificially would 

 require very high initial temperatures. 

 We can not burn sugar by the aid of the 

 oxygen of the air except by reaching first 

 a certain kindling temperature. To burn 

 fats or proteins would be equally difficult. 

 Yet in the animal body, and in the presence 

 of fluids with a mean temperature below 

 40° Centigrade, the oxygen given up from 

 the arterial blood accomplishes these com- 

 bustions continuously and with a regularity 

 corresponding with that of respiration. 

 The theories advanced to account for this 

 oxidation have been many and all more or 

 less unsatisfactory. By some it was sup- 

 posed that the oxygen was first thrown into 

 an active form like ozone, for example. 

 The old Berzelius notion of catalysis was 

 even fifty years ago advanced as a hypoth- 

 esis, but nothing definite was suggested as to 

 the nature of the catalytic agent. It is an 

 interesting fact that after years of fruitless 

 theorizing chemists are coming back to the 

 idea of catalysis, but from a very different 

 standpoint. The peculiar catalyzing agents 

 active in so many ways in the body are now 

 often assumed to be some of the so-called 

 oxidizing ferments or oxidases. The theory 

 of the oxidases is of rather recent develop- 

 ment and there seems to be no question of 

 the existence of these active principles in 

 many vegetable products. Their actual 

 presence in the animal fluids is not so 

 readily demonstrated, but as a result of 

 experiments a great many investigators 



have been gradually brought to accept this 

 idea as a fact. What Ludwig forty years 

 ago pointed out as likely is actually coming 

 to pass. Chemical physiology is becoming 

 largely a study of catalytic reactions. 



Among all the animal oxidations great 

 interest attaches to the combustion of sugar 

 in man. In the digestion of carbohydrates 

 some hexose sugar is finally produced and 

 absorbed and then carried by the portal 

 circulation to the liver. There it is tem- 

 porarily stored up as glycogen, and, as re- 

 quired, is thrown out into the blood stream 

 again to be oxidized for the needs of the 

 body. Normally this oxidation takes place 

 very quickly and no accumulation of sugar 

 in the blood follows. But under certain 

 conditions the oxidation of the sugar be- 

 comes very imperfect or fails entirely, and 

 to maintain the proper osmotic pressure in 

 the blood the excess of sugar escapes by 

 way of the kidneys. This is the situation 

 in the disease known as diabetes mellitus. 

 There are few pathological conditions on 

 which more has been written. We can not 

 say yet that the ultimate cause of diabetes 

 is known, but many facts have been estab- 

 lished by chemical investigation and quite 

 recently the work of Cohnheim has shown, 

 apparently beyond question, that for the 

 normal oxidation of sugar the action of 

 two enzymic bodies of distinctly different 

 origin is required. One of these, as might 

 naturally be expected in the light of earlier 

 knowledge, is furnished by the pancreas, 

 while the other comes from the muscles. 

 The oxidation takes place, or may take 

 place, in the fluid surrounding the muscular 

 fibers. , Cohnheim has shown that the cell 

 structures as such are not concerned in 

 this oxidation, as it may be brought about 

 in clear filtered solutions from mixtures of 

 finely ground muscle and pancreas. It is, 

 therefore, a chemical process and one of 

 the most interesting thus far studied. Not 

 the least interesting and important fact 



