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Appendices to Fifth Annual Report 



water at the bottom. The lid of this chamber fitted tightly, and so the 

 interior could be kept full of saturated water vapour, and evaporation of 

 the contents of the beakers prevented. A small gas flame kept the whole 

 at a temperature of 100° to 105° F., and the contents of the beakers 

 were occasionally stirred. Several trial experiments were made in order 

 to ascertain whether the action of the digestive fluid was ever interfered 

 with by the accumulation of the products of digestion; but when 30 or 

 40 grammes of flesh were put in, the percentage digested from it was only 

 slightly diminished, and in one experiment a large but indefinite quantity 

 of blood fibrin was added and completely digested. 



The amount of material digested was determined by a method so novel, 

 that I quote the author's account of it in full. 'After the gastric juice 

 ' has been allowed to act for the requisite time on the 20 grammes of flesh, 

 'the mixture is cooled to 20° C, and diluted to 250 c.c. in a graduated 

 £ flask, with distilled water. After being thoroughly mixed it is filtered on a 

 ' dry filter, and then 50 c.c, or one-fifth of the entire mixture, is transferred 

 ' by a pipette to a small weighed dish, and to it are added 5 c.c. of a 

 ' standard solution of sodium carbonate of such strength as exactly to 

 ' neutralise the acid present. The fluid is then evaporated to dryness on 

 ' the water bath, and finally dried at 100° C. till of constant weight.' The 

 reason the authors give for discarding the old method of estimating the 

 digestibility, by observing the time taken by various substances to dissolve, 

 is, that the results of that method largely depend on the amount of solid 

 matter in the flesh which is being digested. They give as an instance an 

 experiment performed by Jessen by the natural method. He made a 

 gastric fistula in a dog, and on introducing 2 grammes of the raw flesh of 

 frog's legs he found that it was digested 4*46 hours. The same amount 

 of beef took 5*58 hours under similar conditions. Jessen, apparently 

 assuming that digestibility is proportional to the time taken to digest, states 

 that the digestibility of frog's legs is to that of beef as 84 : 100. Messrs 

 Chittenden and Cummins use a totally different definition of digestibility. 

 They take it as proportional to the amount digested from 20 grammes of a 

 substance after being left for 22 hours in 200 cubic centimetres of the 

 above described digestive solution at a temperature of 100° F. Using 

 this definition they arrive at the conclusion that the digestibility of frog's 

 legs is to that of beef as 80*46 : 100. They compare these figures with 

 those given by Jessen, and explain that the difference is accounted for by 

 the fact that while beef contains 25 per cent, of solid matter, frog's legs 

 only contain 17 per cent. That this is the true explanation does not 

 seem probable. It is more likely that the differences in the results are to 

 be explained by the very different definitions adopted. Neither of the 

 above ways of defining digestibility is good; for Jessen's definition is 

 really a definition of indigestibility, the inverse of digestibility, and with 

 regard to Messrs Chittenden and Cummins' definition any dyspeptic will 

 tell you that it is a matter of almost vital importance to him whether his 

 stomach can extract the nutriment from a given sample of food in two 

 hours or in twenty-two. That Messrs Chittenden and Cummins' results are 

 not altogether independent of the amount of solid matter in the fish being 

 digested is shown by a glance at Table II. There the amount of fat in 20 

 grammes of each kind of fish as determined by Professor Atwater is sub- 

 tracted from the amount of solid matter in 20 grammes as determined by 

 Chittenden aud Cummins. What is left is of course the amount of proteids 

 and salts in 20 grammes, that is the amount of solid matter capable of being 

 dissolved by the gastric juice. When this is compared with the amounts 

 actually digested from 20 grammes, a most remarkable correspondence, 

 considering the uncertainty of the data, is found between them. 



