126 



EXERCISE XX 



ANNOTATION 



Ohs. 91, 92. In this exercise you repeat 

 the fundamental experiment by Bayliss and 

 Starling, 1902 {Proc. Roy. Soc. vol. Ixix, 

 p. 352 ; Jnl. of Physiol, vol. xxviii, p. 324), 

 discovering the hormone 'secretin'. The 

 action of the acid on the duodeno-jejunal 

 mucosa produces a substance secretin, which 

 when circulated with the blood-stream ex- 

 cites secretory activity in the pancreas. It 

 forms much the most potent, and almost the 

 only, means of exciting pancreatic secretion. 

 For such excitant 'chemical messengers', 

 Bayliss and Starling, at suggestion of W. B. 

 Hardy, introduced the term hormone. 



For an analogous ' hormone ' from stomach 

 (gastrin), see Edkins, Jnl. of Physiol, vol. 

 xxxiv, p. 133, 1906. The hormones form in 

 Schafer's nomenclature the excitant group of 

 the 'autacoids' (Endocrine Organs, London, 



1916) ; but see Bayliss, Principles of Gen. 

 Physiol, p. 709. For secretin consult the 

 above-mentioned original papers by Bayliss 

 and Starling ; also Starling, Proc. Roy. Soc. 

 Med. vol. vii, p. 29, 1914; and Bayliss, 

 Principles of Gen. Physiology, 2nd ed., 

 pp. 708-12, 1918. For pancreatic excitants 

 other than secretin, see Gley, Jnl. dephysiol. 

 gdnerale, vol. xl, p. 509. 



In relation to § IV of this exercise, it is 

 well not to carry the ' neutralization ' to full 

 completeness lest the neutral point be over- 

 stepped. If the solution become alkaline it 

 is more difficult to filter even if reneutra- 

 lized by adding more acid ; and, further, 

 secretin is easily destroyed by boiling in 

 alkaline solution. 



Obs. 93. For ' bladder-bile ', consult any 

 text-book. 



EXERCISE XXI 



PHAGOCYTOSIS AND ESTIMATION OF OPSONIC INDEX 



I. See that the decapitate preparation provided on the warm table is in 

 good condition and being properly ventilated bj the ' blower '. 



II. Three things are required, viz. and you wiU yourself prepare them : 



1. the sera : 



[a] normal or control ; 



{b) the serum whose index it is desired to estimate. This may 

 be termed ' patient's serum ' ; it will be, in this exercise, the 

 normal serum inactivated, or partly so, by heat. 



2. washed leucocytes; 



3. an emulsion of the bacteria in -9 per cent. NaCl ; 



