January 2, 1885.] 



SCIENCE. 



11 



of the ridge, the neighboring peaks rose around them ; 

 and all New Zealand, from western to eastern coast, 

 with the ocean beyond on either side, lay below. The 



THE TOP OF MOUNT HOCHSTETTEK. 



story of the journey is simply and graphically told, 

 and suggests a writer of more intelligence and better 

 powers of observation than is usually met with among 

 mountain climbers. 



THE DIGESTIBILITY OF CELLULOSE. 



It is a well-established fact, that a considerable por- 

 tion of the woody fibre which is consumed in such 

 large amounts by herbivorous animals does not re-ap- 

 pear in their excrements, but is apparently digested. 

 In what portion of the alimentary canal, or by means 

 of what secretion, this digestion is accomplished, has 

 been the subject of much speculation and of some 

 experiments; but, until recently, neither had done 

 much to illuminate the matter. 



Hofmeister 1 seemed to have gone far towards solv- 

 ing the question when he found that a considerable 

 solution of the cellulose of grass took place in the 

 rumen of sheep. He first enclosed two small samples 

 of fresh grass in cages of german-silver wire covered 

 with muslin, and introduced them into the rumen of 

 a living sheep. After three days the animal was 

 killed, the cages removed, and their contents exam- 

 ined. It was found that seventy-eight and four-tenths 

 per cent of the woody fibre originally present had 

 been dissolved. Subsequent experiments showed that 

 the fluid obtained from the rumen of a freshly killed 

 sheep had also a powerful solvent action on woody 

 fibre, and that the mixed saliva had likewise this 

 power. Experiments on oxen gave no decisive result : 

 those on the horse failed to show any solvent action 

 of the saliva upon woody fibre. Hay, and the ' crude 

 fibre ' prepared in the analysis of fodders, were acted 

 upon by the fluid from sheep's rumen, though not so 

 energetically as was the grass. 



These results point unmistakably to the first stom- 

 ach of ruminants as one place where cellulose is 

 digested. Hofmeister ascribes to the mixed saliva 

 the power of dissolving it; but some subsequent ex- 

 periments by Tappeiner 2 indicate that this is effected 

 by a fermentative process, and that the saliva or fluid 

 from the rumen used by Hofmeister served simply 

 to supply food to the organisms concerned in the 



1 Biedermann'a centralblatt, Jahrg. x. p. 669. 



2 Thier. chem. her., xi. 303, xii. 266 and 272; Zeitsc/tr. fur 

 Hologie, xx. ~>2. 



fermentation. Tappeiner took samples of the con- 

 tents of rumen, small intestine, and large intestine. 

 of a ruminant fed exclusively on hay. One sample 

 from each portion of the alimentary canal was at 

 once boiled ; to a second some antiseptic (chloroform, 

 thymol) was added, sufficient to stop the action of 

 organized ferments; while to the third nothing was 

 added. All were kept warm, and after a time their 

 content of crude fibre was determined. Those por- 

 tions from the rumen and large intestine, to which 

 nothing was added, were found to have lost cellulose, 

 while carbonic acid and marsh-gas were evolved. No 

 loss was observed from the contents of the small intes- 

 tines, nor from the samples treated with antiseptics. 

 Further experiments showed that this fermentation 

 could be produced outside the body. To hay or pure 

 cellulose, mixed with extract of meat, and previously 

 heated to 110° C, a drop of fluid from the rumen 

 was added. After a few days, active fermentation 

 began. Gas was freely evolved, consisting of about 

 seventy-six per cent of carbonic acid and twenty- 

 four per cent of marsh-gas, and the cellulose nearly 

 all disappeared. A second kind of fermentation was 

 also observed, which yielded carbonic acid and hydro- 

 gen. In both kinds of fermentation, only the smaller 

 part of the cellulose was volatilized, most of it being 

 converted into acids of the fatty series. 



That cellulose is fermentable is not a new obser- 

 vation ; Van Tieghem having found that the butyric 

 ferment has the power of decomposing it, with pro- 

 duction of hydrogen, carbonic acid, and butyric acid. 

 Tappeiner' s experiments are of interest, because they 

 show that the fermentation takes place also in the 

 alimentary canal. This is shown not only by the 

 disappearance of the cellulose in the experiments 

 described above, but also by the presence of the prod- 

 ucts of the fermentation in stomach and intestines. 

 In ruminants the marsh-gas fermentation seems to 

 prevail. In the stomach of the horse and swine 

 considerable quantities of hydrogen were found. In 

 both cases acetic acid, aldehyde, and an acid hav- 

 ing the composition of butyric acid, were found. 



These results are important in their bearing on our 

 estimates of the nutritive value of fodders. It having 

 been shown that the digestible portion of the crude 

 fibre has the composition of starch, it has generally 

 been assumed to have the same nutritive value. Tap- 

 peiner' s experiments show that this is probably not 

 the case. There appears to be a disposition on the 

 part of some critics, however, to rush to the opposite 

 extreme, and, instead of overestimating the nutritive 

 value of cellulose, to underestimate it.- The non- 

 nitrogenous nutrients are to be regarded as the fuel 

 of the body, and they are of worth to it in proportion 

 to the amount of energy set free by their oxidation 

 to carbonic acid and water. So far as we can see, it 

 is a matter of indifference whether that oxidation 

 begins in the alimentary canal, or not until the sub- 

 stance has passed into the circulation. Whatever 

 potential energy is contained in the digested cellulose 

 is yielded up to the body sooner or later, with the 

 exception of that portion which escapes in the form 

 of combustible gases. According to Tappeiner. this 



