96 LABORATORY MANUAL OF GENERAL PHYSIOLOGY 



Note: If fresh water mussels are studied use mussel Ringer (NaCl 0.12%, CaCh 0.012%, 

 KCl 0.015%, pH 7.8). Excess KCl arrests these hearts in diastole (cf. Motley Physiol. 

 Zool., 7: 62, 1934). According to Kock, Pfliigers Arch., 156, 1916, excess K or Ca causes 

 systolic standstill in heart of Anodonta. 



DEMONSTRATION 



Oscillograph Recording of Action Cixrrent in 

 the Heart. — A frog's heart is placed on cotton 

 points soaked in Ringer leading to non-polariza- 

 ble Ag-AgCl electrodes connected to an ampli- 

 fier which magnifies the potential changes 

 recorded by an iron tongue oscillograph and 

 loud speaker. 



XV. COMPARATIVE PHYSIOLOGY OF 

 RESPIRATORY PIGMENTS 



Haemoglobin is the best-known of the 

 pyrrole pigments of animals and consists of a 

 protein portion, a dyestufF (prosthetic group) 

 containing iron. The following directions are 

 taken from Cannon's "Laboratory Course in 

 Physiology," by kind permission of Harvard 

 University Press. For a brief account of oxygen 

 transporters in various animals cf. Florkin, 

 "Transporteurs d'oxygene," Hermann, Paris, 

 1934; Roche, "Biochemie des pigments respira- 

 toires," Masson, Paris, 1935. Text pp. 412-413. 

 1. Determination of Carbon Dioxide Dissoci- 

 ation Curve of Ox Blood. — A blood-gas pump 

 Fig. 9.-Blood-gas pump, ^as as an essential feature a reservoir which can 

 A, cup for blood sample; B, be filled with mercury, and after its connections 

 :^ZcZTi^t,Tor%B, have been tightly closed can have a vacuum 

 upper stem of pipette marked developed w^ithin it by the withdrawal of the 

 SS.rpSn'il'f s^ifoiJt ■nercury. A simple apparatus o£ this character 

 comiecting E with G or H; G, is that devised by Van Slyke (Van Slyke, J. 

 LrieS^.*"/he'°4trS Biol. Chem., 30: 347, 1917). It consists essen- 

 at bottom is comiected to a tially of a 50 cc. pipette (D, E) (Fig. 9) with 

 mercury leveling bulb. ^ three-way cock at the top (C) and a one- 



way cock at the bottom (F), and a 1 cc. scale on the upper stem of the 

 pipette (D) divided into 0.02 cc. divisions. Below the lower cock is 

 a chamber (H) which serves as a trap for air which may leak in 

 through the connection with the rubber tube below. This tube, which 

 is of heavy-walled rubber, leads to a leveling bulb filled with mercury. 

 The CO2 content of blood is to be determined when it is in equilibrium 

 with gas mixtures (air) containing CO2 at several different pressures. 



