628 



PHYSIOLOGY. 



enters the ventricle, and then rapidly, when the 

 systole of the auricle takes place. On compar- 

 ing these trajectories with the sounds heard in 

 man. and sometimes also in animals, it is found 

 that their amplitude is greatest when these 

 sounds are most intense and frequent, that their 

 direction is that calculated to produce in the 

 lung a rapid aspiration during systole, and that 

 the rhythm of the sound is itself in correspond- 

 ence with the variations of speed of the move- 

 ment. The relation thus discovered solves a 

 complex problem of auscultation. 



In the study by C. S. Sherrington and S. 

 Monckton Cope of the variations experimentally 

 produced in the specific gravity of the blood, the 

 method employed determined only the specific 

 gravity of the blood considered as a mixed and 

 complicated whole. What particular factor, or 

 factors, in each case caused an alteration in the 

 specific gravity remains to some extent a matter 

 of conjecture. The alteration might be due to 

 one, or two, or all, of the following causes : An 

 increase or diminution in the number of corpus- 

 cles in a given volume, the specific gravity of in- 

 dividual corpuscles and of the plasma remaining 

 unchanged ; an increase or diminution in densi- 

 ty of the plasma, the specific gravity and the 

 number of the corpuscles remaining unaltered ; 

 or a simultaneous increase or diminution in densi- 

 ty both of corpuscles and plasma, with or with- 

 out alteration in the number of corpuscles in a 

 given volume of the blood. When a quantity of 

 normal saline solution is injected rapidly into the 

 circulation, the specific gravity of the circulating 

 blood is at once diminished, but the diminution 

 persists for a short time only. It is attributed 

 to the speedy escape from the circulation of the 

 saline injected, feepeated injections of small 

 quantities of saline solution into the vascular 

 system do not perceptibly lower the specific grav- 

 ity of the blood unless the interval of repetition 

 be very small relatively to the amount injected. 

 And e'ven in the latter case no permanent dilu- 

 tion of the blood is brought about. By contin- 

 ued injection the blood of the rabbit may be kept 

 for more than an hour at a degree of dilution 

 nearly amounting to what would be reached by 

 admixture with it of an equal volume of water, 

 and this dilution is maintained without produc- 

 tion of devious signs of circulatory, respiratory, 

 or nervous distress. By observation of the al- 

 teration of specific gravity a means is obtained 

 for gauging the volume of blood in the circula- 

 tion of the animal receiving the injection. This 

 volume in a well-fed adult rabbit, dog, or mon- 

 key appears to be somewhat less than 7 per cent, 

 of the total weight of the body. The authors at- 

 tempted to repeat the classical observation that 

 during a period of prolonged fasting the blood 

 shares but slightly in the wasting of bulk under- 

 gone by the tissues of the body as a whole. The 

 conditions that influence the passage of water 

 through living animal membrane are intimately 

 dependent upon characters associated with the 

 membrane considered as protoplasm, or material 

 endowed with life. Toward the end of a long 

 experiment it is extremely common to find that 

 the specific gravity of the blood becomes lower, 

 and when death occurs this diminution may 

 amount to 2 or 3 units in the third place of deci- 

 mals. The explanation of this is not clear, but 



there are considerations that may throw light 

 upon it, such as the appearance of local differ- 

 ences in specific gravity very soon after death 

 and the clotting that rapidly sets in in the larger 

 vessels. The slightest pressure on the splenic 

 vein induces a rise in the specific gravity of the 

 blood, the accompaniments of which are" similar 

 to the symptoms which surgeons associate with 

 shock. A considerable quantity of water can be 

 transferred from one part of the body to anoth- 

 er, presumably by means of the circulation, with- 

 out any obvious dilution of the blood. The effect 

 of withdrawing any considerable quantity of 

 blood from the circulation is to make the remain- 

 ing blood poorer in solid matters. Notwithstand- 

 ing the , observations of Lloyd Jones and J. <J. 

 Otto, the authors have found the differences in 

 the specific gravity of venous and arterial blood 

 so slight as to leave the existence of an actual 

 difference doubtful. That the important factor 

 in the inspissation of blood in an area of ob- 

 structed venous flow is not the mere distention 

 of the capillaries and venous radicles and veins, 

 and the heightened pressure in them, seems in- 

 dicated by the very different effect on the specific 

 gravity which section of the cervical spinal cord 

 occasions. Such section causes venous conges- 

 tion of the great splanchnic region of the circu- 

 lation. Yet so far from giving an increase in the 

 specific gravity of the blood, it is an operation 

 followed by a fall in the same. Local differences 

 are observed in the specific gravity of the blood, 

 and seem to be connected with differences in vaso- 

 constriction. 



The influence of great heights on the constitu- 

 tion of the blood has been studied by M. Viault 

 and M. Muntz, whose conclusions are alike. The 

 blood of rabbits taken from the plain to the top of 

 the Pic du Midi and kept there for seven years had 

 a respiratory capacity nearly double the normal 

 (17 cubic ce'ntimetres to 9). The proportion of 

 metallic iron was also raised from 40 percent, to 

 70 per cent., indicating a corresponding aug- 

 mentation in haemoglobin. A long stay a.bove 

 is not necessary to produce these changes. Sheep 

 in the Pyrenees, which are taken up the moun- 

 tains every summer, show them in a few months. 

 Even the mountains are not required, for M. 

 JVIuntz has shown that the same result is brought 

 about by increasing the proportion of combus- 

 tible food consumed by the animal. 



The researches of Dr. B. Levy on the circula- 

 tion of the blood in the brain give results con- 

 tradictory to those reached by Geigel, which 

 were that constriction of the arteries produces 

 an increased blood supply, and their dilatation 

 causes the supply to decrease. Dr. Levy insists 

 that physiological supply of blood to the brain 

 is regulated in the same way as in all other or- 

 gans that is, that the dilatation of arteries pro- 

 duces an increase, and their constriction a de- 

 crease, in the current of the blood. Venous 

 congestion leads to arterial anaemia. Acute com- 

 pression of the brain caused, for instance, by a 

 foreign body penetrating the skull and dilata- 

 tion of arteries beyond certain limits, as by in- 

 flammation, have a'like effect. Extensive deple- 

 tion of the capillaries leads to a perversion of the 

 blood supply. Dilatation of the arteries, then, 

 produces anaamia, while contraction leads to hy- 

 persemia. The supply is consequently not influ- 



