434 THE PRESERVATION OF NEUTRALITY 



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 j;H = 7-4. 



Alterations caused. 



1. Tending towards alkalinity — Alkaline tide after digestion. 



2. Tending towards acidity. 



A. Normal. (1) Muscular activity. COo. 



Lactic acid. 

 (2) Protein disintegration, food fHoS04 



muscle [P2O5 



B. Abnormal. Mal-oxidation acidosis. 

 Alterations checked. 



1. Tissue compensation — Phosphates. 



2. I Alkali reserve^ — NaHCOa. 



^ ' ... ( COo stimulates respiratory centre. 



3. Respiration ' " „ „ ^^ , ^ 



y ^ \ Lack of free LU, depresses centre. 



, ,^. T la) increased elimination of -< „ -,. : as salts. 



4. Kidney - ^ ' alkali ; 



[(/^) NH3 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 pH. in spite 

 of additions of acid or alkali. The late Professor 8ir Wm. 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. 



