482 AN AMERICAN TEXT-BOOK OF PHYSIOLOGY. 



heart working under a load of 3.5 centigrams, and under an " after-load " of 3 

 centigrams in spontaneous activity for more than twenty-four hours. The 

 sustaining action which dextrose appears to exercise is shared, according to him, 

 by various other organic substances. 



Physical Characteristics. Heifter 1 and Albanese, 2 having observed that 

 the addition of gum-arabic to the circulating fluid was of advantage, declared 

 that the nutrient solutions should possess the viscosity of the blood. The 

 favorable action of gum-arabic may, however, more probably be ascribed to the 

 compounds which it contains rather than to its physical properties. 3 



Mammalian Heart. The success attained within the past two years in the 

 isolation of the mammalian heart opens up an hitherto unexplored region in 

 which systematic investigation will surely bring to light facts of wide interest 

 and value. At present, however, little is known as to the constituents of the 

 blood which are essential to the life of the mammalian heart. An abundant 

 supply of oxygen is certainly highly important. 4 



Blood of Various Animals. Roy 5 gives some data as to the effect on the 

 frog's ventricle of the blood of various animals. The blood of the various her- 

 bivora (rabbit, guinea-pig, horse, cow, calf, sheep), as well as that of the pigeon, 

 were found to have nearly the same nutritive value in each case. That of the 

 dog, of the cat, and more especially of the pig, while in some instances equal in 

 effect to that from the horse or rabbit, were in other examples (from the newly 

 killed animals) apparently almost poisonous. Cyon's early observation of the in- 

 jurious action of dog's blood on the frog's ventricle has already been mentioned. 



Regarding the mammalian heart, experience has shown that it is best to 

 supply the heart with blood from the same species of animal. 7 The difficulties 

 attending the use of blood from a different species are seen in the case of the 

 dog's heart supplied with calf's blood. The heart dies sooner ; oedema of the 

 lungs takes place, impeding the pulmonary circulation and leading to engorge- 

 ment of the right heart and paralysis of the right auricle ; exudation into the 

 pericardium often seriously interferes with the beat of the heart; and, finally, 

 the elastic modulus of the cardiac muscle is apparently altered, permitting the 

 heart to swell until it tightly fills the pericardium, when the proper filling of 

 the heart is no longer possible through lack of room for diastolic expansion. 



PART IV. THE INNERVATION OF THE BLOOD-VESSELS. 



About the middle of the eighteenth century more or less sagacious hypotheses 

 concerning the contractility of the blood-vessels began to appear in medical 



1 Heflter, 1892, p. 52. a Albanese, 1893, p. 311. 



3 Howell and Cooke, 1893, p. 216 ; Locke, 1895, p. 333. 



4 Experiments on the artificial circulation of defibrinated blood through the coronary arter- 

 ies have been performed by Martin and Applegarth, 1890, p. 275; Arnaud, 1891, p. 396; 

 He*don and Gilis, 1892, p. 760; Langendorff, 1895, p. 291; Porter, 1896, p. 46; Magrath and 

 Kennedy, 1896. 5 Hoy, 1879, p. 460 ; compare Heffter, 1892, p. 44. 



6 Cyon, 1867, p. 89. 7 Martin, 1883, p. 676 ; see also Langendorff, 1895, p. 293. 



