NA TURE 



597 



THURSDAY, AUGUST 23, 1894. 



1 THE PHYSIOLOGY OF THE CARBO- 



I HYDRATES. 



1 The Physiology of the Carbohydrates : their Applica- 

 tion as Food, and Relation to Diabetes. By F. W. Pavy, 

 M.D., F.R.S. (London : Churchill, 1894.) 



\MONG the most debated subjects of physiology the 

 ultimate fate of carbohydrates within the body 

 stands out as one of the greatest difficulty. A great 

 jamount of work has been expended on it, but still many 

 Ipoints of vital importance remain undecided. We 

 [accordingly hail with pleasure a work containing the 

 results and conclusions of one whose name is indisso- 

 lubly associated with the subject, as the author of one of 

 the two rival theories around which much of the work of 

 the last thirty years has centred. The book before us 

 jcontains a revised description of the many researches 

 of the author upon this subject, with a criticism of his 

 earlier results by the light of his later work, and the 

 greatly increased knowledge of the chemistry of the 

 carbohydrates which is now available. Embodying as it 

 does the results of a " life's labour, attended with unceas- 

 "■_' laboratory work," we turn to it with more than 

 linary interest. 



The book is arranged in sections, in the first of which 



the author gives us a short account of the main chemical 



characters of the principal carbohydrates, and special 



-tress is laid upon the production of osazones as enabling 



us to distinguish the different sugars from one another. 



This is followed by an account of the hydrations produced 



by ferment action and the changes known to occur 



•ii rough the agency of protoplasm. Succeeding sections 



1 almost entirely with Dr. Pavy's researches, arranged 



in the order in which they appeared, but in such a 



nner as to gradually unfold the author's argument. 



I bus we find described the experiments upon which he 



xludes that many proteids have the constitution of 



M osides. Next the path of absorbed sugar is traced 



he liver, and his experiments proving its conversion 



into glycogen are given. Many experiments upon the 



iinounts of sugar present in arterial and venous blood, 



in blood from the portal and hepatic veins, and in the 



' cr and other tissues, are given, as well as quantitative 



lilts of the amount of glycogen and other carbohy- 



(drates present in these positions. The sugar in urine is 



'next discussed, and here he brings evidence to prove that 



inal urine contains sugar. 



I >r. Pavy for his quantitative results relies almost en- 

 tirely upon the ammoniated cupric solution, and con- 

 tends that the results obtained by its careful use are 

 ili'ioughly trustworthy. Where he gives duplicate esti- 

 mations, however, we note that there are often consider- 

 able differences in the two values obtained. Thus, his 

 figures give a further confirmation of the difficulty, if not 

 impossibility, of obtaining very accurate results as to the 

 quantity of sugar present in a solution, by means of a 

 standard copper solution. It is of essential importance 

 to keep this constantly in mind in those cases, such as 

 determination of the quantity of sugar in blood from 

 portal and hepatic veins, or from carotid artery and 



NO. 1295, VOL. 50] 



jugular vein, in which the results, which we know must be 

 very close to one another, are to be compared. For this 

 reason especially we do not consider that Dr. Pavy has 

 satisfactorily established his position, though it is a most 

 important one for his further conclusions. 



His experiments upon the glucoside constitution of 

 proteids are very suggestive and important, but before 

 they could be conclusive it would be necessary to pay 

 much greater attention to the proper purification both of 

 the proteid with which he starts and the " cleavage car- 

 bohydrate " which he obtains, and to give quantitative 

 analyses of this latter body. For instance, in the case of 

 egg albumin, which is one of the bodies he uses, we 

 know that it contains a considerable amount of glycogen, 

 and that it is extremely difficult to completely free the 

 proteid from it. But as this latter point does not seem 

 to have been thoroughly attended to in these experiments, 

 we must await further corroboration. 



There are many other points about which we expect 

 much discussion may arise, and among these we may 

 mention his conclusions — firstly, that sugar is present in 

 urine ; and secondly, that it is present in proportion to the 

 amount present in the blood. In connection with the 

 first of these two points we would refer to the recently 

 published paper of Carl Baisch,' who uses the benzoyl 

 chloride method, which is certainly to be regarded as 

 capable of producing more accurate results than the use 

 of the copper test. He, in confirmation of Dr. Pavy, 

 finds that a reducing carbohydrate is present, and he 

 further shows that dextrose is present to the extent of 

 04 to 09 per 1 000 of urine, total-reducing carbohydrates 

 amounting to as much as 06 to "16 per 1000. Dr. Pavy, 

 on the other hand, finds a much larger quantity, which, 

 calculated as glucose, he states, amounts to as much as 

 ■5 per 1000. 



Now, if we compare the figures given on page 1 89 as 

 to the amount of sugar present in urine as a consequence 

 of an abnormal small excess in the blood, with the result 

 he gives as present in normal urine, we cannot, from their 

 study, at all agree that these amounts are proportional to 

 that present in the blood. Still less would this conclu- 

 sion be acceptable were we to take the above-quoted 

 figures of Baisch. 



Perhaps the conclusions upon which Dr. Pavy would 

 lay by far the greatest amount of stress is that the major 

 part of the sugar absorbed from the alimentary canal is 

 immediately combined with the peptone simultaneously 

 absorbed to form a proteid, which is then transmitted 

 to the general circulation, and thus to the tissues gener- 

 ally. Dr. Pavy considers that this synthesis is in part 

 effected by the epithelial cells covering the villi. Under 

 one set of conditions, viz. defective oxidation, &c., this 

 proteid may break down and result in the production of fat, 

 or again under another set, e.g. excessive oxygenation of 

 the blood associated with vaso-dilatation, a second form of 

 katabolism is produced, characterised by the production of 

 sugar, which is then eliminated in the urine. Before, how- 

 ever, we can accept these views it will be necessary that 

 much of Dr. Pavy's work should be corroborated. It is of 

 course known, that under the right conditions within the 

 body, fat or sugar can be formed as a result of unusual 

 proteid katabolism ; but that proteid is usually syn- 



' Zeit. fur Physiol. Clicmic, xix. p. 357. 



s 



