736 



PHYSIOLOGY. 



at any part of its course an alteration which 

 will travel with the velocity of the blood stream, 

 and be capable of easy recognition at any other 

 part. Among the advantages of the method are, 

 that it does not affect the vascular system except 

 at one selected point; that the only substance 

 introduced into the blood is a harmless salt, 

 which is already present there, and is rapidly 

 eliminated ; that it admits of a rapid succession 

 of observations on the same animal ; that it lends 

 itself to determining the circulation in individual 

 organs or tissues under different conditions; "and 

 that it is specially suited for small animals. 



Phosphate of lime has been found by Sidney 

 Ringer superior in qualities to calcium chloride as 

 an ingredient in an artificial circulating fluid. As 

 between the various solutions named, in respect 

 to their efficiency to sustain contractility of the 

 heart, comparative experiments showed that sa- 

 line solution is least effective ; saline containing 

 sodium carbonate is next in order ; then phos- 

 phate of lime saline; and next, phosphate of 

 lime saline containing potassium chloride. When 

 sodium bicarbonate is added to the saline, the 

 composition is stronger in the midwinter months. 

 Hence lime and potash salts appear to be as ne- 

 cessary to the metabolism of muscle at rest as to 

 the metabolism occurring during a muscular con- 

 traction. While the author finds that the alka- 

 line-soda salts do not play so important a part in 

 the production of the contraclions as Biedermann 

 supposed, both authors agree that temperature 

 strongly influences the contractions. At a low 

 temperature these movements become somewhat 

 rhythmical. From comparative experiments with 

 a number of other salts, the inference is drawn 

 that substances of that nature in part sustain 

 contractility by preventing or lessening the 

 twitching of the muscles. 



From experiments made to ascertain the nerve 

 centers for respiration. Dr. Laborde found that 

 superficial mechanical injury to the region of the 

 alae cinerea? does not accelerate respiration ; if 

 the injury penetrates at least to the middle of the 

 substance, respiration may cease altogether. This 

 result is always obtained if a certain circumscribed 

 portion of the substance is cauterized with the hot 

 iron. The iron must, however, enter immediately 

 above the apex calami, and must penetrate at 

 least half the substance from the raphe. If the 

 injury is unilateral, respiration may continue for 

 some little time on the opposite side. Total sepa- 

 ration of the medulla below the apex calami al- 

 ways arrests respiration of the trunk, while that 

 of the head continues for some time. Spinal 

 reflexes continue, and even increase; irregular 

 superficial contractions of the respiratorymuscles, 

 leading to no results, may be observed. The in- 

 crease of the reflex action is especially remark- 

 able in new-born animals. 



It has been shown by Dr. Marcetthat different 

 persons respire different volumes of air to furnish 

 to the body the oxygen required, and to yield 

 a given weight of carbonic acid. Thus, to pro- 

 duce one grain of carbonic acid, three persons 

 were found to need, on an average, 9-29, 1CH51, 

 and 11'30 litres of air, respectively. The first was. 

 twenty-three years of age, the third sixty. The 

 influence of food on the formation of carbonic 

 acid in the body begins in the first hour after a 

 meal, and increases for two or three hours, the 



period of maximum respiration of carbonic acid 

 varying in this time. After a certain time the 

 weight of carbonic acid expired decreases more 

 rapidly than the required volumes of air decrease. 

 The influence of local variations of air pressure 

 appears in less air being needed foi a given 

 amount of carbonic acid with low pressures than 

 with high ; but the degree of the influence varies 

 in individuals. 



From experiments in elevated regions of South 

 America, M. Viault finds that the proportion of 

 oxygen contained in the blood of men and ani- 

 mals (indigenous or acclimatized) living in the 

 rarefied air of mountainous regions is sensibly 

 the same as that which is contained in the blood 

 of men and animals living at lower levels. Both 

 he and Mr. A. Mimtz find that animals living at 

 great altitudes that is, in a medium where the 

 pressure of oxygen is low have the proportion 

 of hemoglobin in the blood increased ; whereby 

 the blood acquires an absorbing power for oxy- 

 gen which compensates for the effect of rarefac- 

 tion. Altitude is not necessary to produce these 

 modifications, but the same results may be ob- 

 tained if. instead of diminishing the amount of 

 oxygen, the quantity of combustible matter is in- 

 creased. 



The researches of Mr. Raphael Dubois have 

 led him to the conclusion that the production of 

 light in animal organisms is due to the trans- 

 formation of the colloidal protoplasmic granula- 

 tions into crystalloidal granulations, taking place 

 under the influence of a respiratory phenomenon. 



Prof. T. P. A. Stuart has determined by ex- 

 periments with rings of crinoline steel that the 

 form of the thorax is determined in part by grav- 

 itation. The shape of the thoracic segment of 

 the quadruped, of the human foetus, and of the 

 human adult are reproduced in succession if the 

 ring be held between finger and thumb and 

 turned, from lying in the vertical, till it lies in 

 the horizontal plane. The complete reproduc- 

 tion of the different features of the adult hu- 

 man thorax at its most characteristic level is 

 striking. The author's hypothesis was also borne 

 out when deformities were imitated by holding 

 the rings under abnormal modes of suspension. 



Digestion. An investigation is described by 

 R. H. Chittenden and J. A. Hartwell. the object 

 of which was to obtain some positive data re- 

 garding the relative formation of albumoses and 

 peptones in artificial gastric digestion. The ex- 

 periments showed that the formation of peptone 

 is a gradual process, and that the greater part of 

 the peptone formed by the action of pepsin- 

 hydrochloric acid passes through the stage of 

 aibumose or proteose, and that at the end of the 

 most vigorous gastric digestion a considerable 

 part of the proteid digested will be in the form 

 of proteose. The authors are not able to say to 

 how great an extent it will be necessary to mod- 

 ify these conclusions in applying them to the 

 proteolytic changes of natural digestion. 



The nature of the change undergone by gela- 

 tin when, under the influence of gastric and 

 pancreatic juice, it becomes liquid and loses the 

 power of gelatinization, has been investigated by 

 R. H. Chittenden and Fred. P. Solley. The 

 results of the investigation showed that three 

 products are formed in the digestion of gelatin 

 with gastric and pancreatic juice, two of which 



