The absolutely and relatively refractory phases of these fibers have been determined by plotting the curve of return of irritability after a maximal first stimulus. The potentials were recorded after conduction to allow separation out from the earlier waves (Gasser and Erlanger) .3 Condenser charges were employed usually up to 160 volts and from .01 to .1 microfarad capacity. These condensers were connected through 2 contacts of the circuit breaker and charged in series with the bridge containing the nerve, the whole being balanced for capacity and resistance. T o prevent the first condenser shunting the second, the circuit breaker was made to open the first circuit before the second was closed, the condenser charging through the nerve circuit during this interval. Both repeated and single pairs of stimuli were employed and it was found that stimuli applied more frequently than at the rate of 1 per second resulted in a prolongation of the absolutely refractory phase. The nerve was supplied with oxygen at room temperature. Preliminary experiments on the effect of anoxemia on these fibers and the knowledge that in the ordinary myelinated fibers, failure of response occurs when the normal absolutely refractory period of less than one sigma has increased only 100 to 30076, both indicate that the long absolutely refractory period found for these fibers is not the result of depression by anoxemia. They have an absolutely refractory period of 4 to 6 sigma when the action potential is still maximal, as indicated by the results of single stimuli.These measurements of the properties of the unmyelinated fibers are being used to differentiate between types of fibers found in the same nerve.Blood 'sugar values obtained by Somogyi's' fermentation technique very probably represent the trzle sugar of blood. This procedure, while the standard for comparison, is somewhat laborious, r, Gasser, H.
HARDING AND SELBY [1931] have recently published extensive observations on the output of fermentable sugar in normal urine. Their report prompts us to record some findings made in this laboratory during recent years. Our plan has been to study the daily excretion of both fermentable and nonfermentable sugar by normal individuals and with these data for comparison to investigate various factors which influence the excretion.As will be noted from the introduction of the paper by Harding and Selby the question of a suitable method of analysis is paramount in an investigation of this kind. This is especially true when determination of non-fermentable as well as fermentable sugar is involved. Here the efficient pre-treatment of the urine to remove non-sugar reducing substances is imperative. Precipitation with mercuric nitrate-sodium bicarbonate according to Benedict and Osterberg [1918] is probably the most efficient treatment which has been reported in the past, yet this method has the disadvantage of leaving a high salt concentration in the filtrate and there is danger of adding too much bicarbonate with resulting oxidation of sugar by the mercuric ion. Treatment with Lloyd's reagent which was introduced by Folin and Berglund [1922] and which has been used in various ways by different workers, according to our experience, leaves much non-sugar reducing material. In order that maximum accuracy be obtained it is also advisable to use a sugar method capable of estimating small quantities.Preliminary to their studies, the writers have developed a procedure of analysis for fermentable and non-fermentable sugar in urine which seems to them to represent an improvement over former methods. It is based upon three procedures. Filtrates of urine are prepared by the HgSO4-BaCO3 technique of West, Scharles and Peterson [1929] which has been found effective in removing interfering nitrogenous substances from biological fluids without introducing appreciable amounts of electrolytes and without loss of sugar.
THE first paper of this series by West and Peterson [1932] outlines an improved procedure for the determination of fermentable and non-fermentable sugars in urine. Although a number of workers have studied the factors which influence the excretion of these substances, the whole question is in a rather confused and unsatisfactory state. This is largely due to the fact that in much of the older work the methods of analysis were inadequate. This applies especially to the fermentation procedures used, which involved the use of unwashed yeast acting for many hours. Under such conditions it is well recognised that the yeast itself may add an amount of reducing material which may completely offset that removed by the yeast, leading to data which indicate the complete absence of fermentable sugar, or bacterial contamination may cause sugar destruction leading to values for fermentable sugar which are too high. Other sources of error lie in the incomplete removal of non-sugar reducing substances from the urine before analysis and the use of sugar methods incapable of detecting small differences. Benedict and Osterberg [1918] using Hg(NO3)2-NaHCO3 filtrates of urine and the picrate sugar method, studied the effect of diet and starvation upon the excretion of total sugar in the dog. They found this to be highest on a carbohydrate diet, appreciably decreased on a high protein diet and markedly less during starvation. They noted a maximum excretion 4-5 hours, and a minimum excretion about 15 hours, after feeding. They found the output to be independent of urine volume. These workers with Neuwirth [1918] studied both the fermentable and non-fermentable sugars in the urine of two normal men as affected by diet. They found the total excretion to be greater, in general, for a high carbohydrate than for a high protein diet, both fermentable and nonfermentable fractions being increased. Their fermentable values for all experiments on one individual averaged nearly the same as their non-fermentable, something over 500 mg. (calculated as glucose) per 24 hours. The other subject
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.