TRANSACTIONS OF SECTION I. 541 



2. The Frequency of Colour-blindness in Men. 

 By F. W. Edkidge-Green, M.D., F.R.C.S. 



Owing to the imperfect methods which have been adopted the percentage of 

 colour-blindness has been much underestimated. Holmgren gave the percentage 

 of the colour-blind as 3'25, but I find at least 6 per cent., and 25 per cent, have 

 diminished colour-perception compared with the remaining 75 per cent. The 

 definitely colour-blind include the dichromic, the trichromic, those who have 

 much shortening of the red end of the spectrum, and those who are unable to dis- 

 tinguish between colours when the image on the retina is diminished in size. 

 Those who have diminished colour-perception include, in addition to the above, 

 the tetrachromic, the pentachromic, and those who have shortening of the violet 

 end of the spectrum, or slight shortening of the red end of the spectrum. 



MONDAY, SEPTEMBER 4. 



Discussion on Ventilation in Confined Quarters, especially in relation to 



Ships. 



(i) Introductory Remarks by Leonard Hill, M.B., F.R.S. 



Carbonic acid up to three to four per cent, of an atmosphere has no note- 

 worthy physiological effect, excepting that it deepens the breathing. Smaller 

 percentages of one to two per cent, are of no account. The breathing of six per 

 cent, produces headache, palpitation of the heart, sweating, and the breathing 

 becomes distressing. Higher percentages, eleven to twelve per cent., produce 

 coma, but do not quickly destroy life. The partial pressure of C0 2 in the pul- 

 monary alveoli and the concentration of acid (hydrogen ions) in the blood is 

 kept constant by the automatic regulatory action of the acid in the blood on 

 the respiratory centre of breathing. 



An atmosphere containing one to two per cent, of CO, simply deepens the 

 breathing to such a degree as to keep the acid concentration in the blood con- 

 stant. Thus, apart from the extra breathing, carbonic acid has no effect on the 

 body (Haldane). Diminution of the partial pressure of oxygen by one to two 

 per cent., and even by three to four per cent., .of an atmosphere, also has no 

 effect, as we see by the fact that men live in health and vigour on high moun- 

 tain plateaux where the partial pressure of oxygen is reduced by one-quarter or 

 even one-third. The great affinity of hremoglobin for oxygen enables man to 

 wander through wide variations of barometric pressure, to quarry mines, and 

 build railways, and execute some of his greatest works at a height of fifteen 

 thousand feet in the Andes. Martin Flack and myself have investigated the 

 composition of the air in the sleeping-chamber of rats. If it is cold outside, the 

 rats prefer to sleep in air containing as much as four to five per cent. CO, and 

 only fourteen per cent. 0,. If the sleeping-chamber is hot and moist, the rats 

 come outside. The discomfort and depressing effect of badly ventilated dwelling; 

 rooms, workshops, schools, and meeting-houses has, therefore, nothing to do 

 with the chemical purity of the air, so far as concerns CO, and 0,, and Haldane 

 has disproved by exact experiment the existence of any poisonous organic 

 chemical matter in the exhaled breath. The ill-effects are mainly due to the 

 effect of the close air on the temperature regulating mechanism and cutaneous 

 nerves. The only reason for maintaining a high standard of chemical purity of 

 the air of dwelling and working rooms is to prevent unpleasant smells arising 

 from dirty clothes, sweat, and floors, and to keep down the mass influence of 

 inferting bacteria. 



Too much importance has been paid to the chemical purity of the air, and 

 not enough to the temperature. It is most necessary to maintain the coolness 

 and movement of the air, for this promotes the metabolism and activity of the 

 body, and by stimulating the cutaneous nerves keeps up the tone of the body. 



Our immunity to disease depends on the quality of the blood, and the supply 



