" BUFFERS " 335 



V. The tissues themselves exert a neutralising effect on the 

 blood. As mentioned above they are endowed with a phosphate 

 buffer system. 



To summarise : 



Blood and tissue fluids normally neutral pH. =7-4. 



Alterations caused. 



1. Tending towards alkalinity Alkaline tide after digestion. 



2. Tending towards acidity. 



A. Normal. (1) Muscular activity. CO 2 . 



Lactic acid. 



(2) Protein disintegration. food \ H 2 SO 4 



muscle J P 2 O 5 



B. Abnormal. Mai-oxidation acidosis. 

 Alterations checked. 



1. Tissue compensation Phosphates. 



2. f Alkali reserve NaHCO 3 . 



R -|TJ . f CO 2 stimulates respiratory centre. 



( Lack of free CO 2 depresses centre. 



(a) increased elimination of <C ,. ras salts. 

 4. Kidney -I v ^alkali } 



[_ (b) NH 3 salts. (Liver action.) 



An apology is necessary for the use of the word " buffer "to denote the 

 power of phosphates and bicarbonates to maintain a steady pR in spite 

 of additions of acid or alkali. Prof. Bayliss has pointed out the misleading 

 nature of this expression and has shown how it crept into use. Non- 

 descriptive as the word undoubtedly is, it has found a place in current 

 physiological and physico-chemical literature, dislodgment from which 

 will be a difficult task. 



