RESPIRA TION. 443 



Lehmann 1 found that there was a distinct lessening of the alkalinity of* the 

 blood after muscular exercise. It is likely that the bodies arc broken up in 

 the system, because the results of Loewy's 2 investigations indicate that they 

 are not removed by the kidneys. 



Polypncea, tiwrmopolyjmoea, and heat-dyspnoea are due to a direct excitation 

 of the respiratory centres through an increase of the temperature of the blood, 

 or reflexlv by excitation of the cutaneous nerves by external heat. This con- 

 dition may be produced, as was done by Goldstein, by exposing the carotids 

 and placing them in warm tubes, thus heating the blood ; or, as was done by 

 Richet and others, by subjecting the body to high external heat. Richet in 

 employing this latter method found that dogs so exposed may have a respira- 

 tory rate as high as 400 per minute. Ott records marked polypncea as a result 

 of direct irritation of the tuber cinereum. This form of hyperpnoea is entirely 

 independent of the gaseous composition of the blood ; moreover, an animal in 

 heat-dvspncea cannot be rendered apnoeic, even though the blood be so thor- 

 oughly oxygenated that the venous blood is of a bright arterial hue. 



Dyspnoea is generally characterized by slow, deep, and labored respiratory 

 movements, although in some instances the rate may be increased. Several 

 distinct forms are observed: " O-dyspnoea," due to a deficiency of O; 

 " C0 2 -dyspnoea," due to an excess of C0 2 in the blood; and cardiac aud 

 hemorrhagic dyspnoeas, belonging to the O category. 



Dyspnoeas due to the gaseous composition of the blood may be caused either 

 by a deficiency of O or by an excess of C0 2 , but are generally due to both. 

 Dyspnoea from a deficit of O is observed when an animal is placed within a 

 small closed chamber, or when an indifferent gas, such as pure hydrogen or 

 nitrogen, is respired. Under the latter circumstances dyspnoea occurs even 

 though the quantity of C0 2 in the blood be below the normal. If, on the 

 contrary, the animal be compelled to breathe an atmosphere containing 10 vol- 

 umes per cent, of CG 2 , dyspnoea occurs, notwithstanding an abundance of O 

 (p. 436) both in the air and in the blood; indeed, the quantity of O in the 

 blood may be above the normal. Fredericq 3 in ingenious experiments has 

 directly demonstrated the influence of the quantity of C0 2 in the blood upon 

 the respiratory movements. He took two rabbits or dogs, A and B, ligated the 

 vertebral arteries in each, exposed the carotids, and ligated one in each animal. 

 The other carotid in each was cut, and the peripheral end of the vessel of one 

 was connected by means of a cannula with the central end of the vessel of the 

 other, so that the blood of animal a supplied the head (respiratory centre) of 

 animal B, and vice versd. When the trachea of animal A was ligated or com- 

 pressed the animal B showed signs of dyspnoea, because its respiratory centre 

 was now supplied with the venous blood from a. On the contrary, animal a 

 exhibited quiet respirations, almost apnoeic, because its centre received the 

 thoroughly arterialized blood from b, in which the respiratory movements were 

 augmented. In a second series of experiments blood was transfused through 



1 Archivfur die gesammte Physiologic, L888, BU 42, S. 284. : Ibid., S. 281 



8 Hull. Acad. roy. Mid. Belgique, t. 13, pp. 417-421. 



