EFFECTS OF DEFICIENT VENTILATION. 185 



operations were carried on, the gradual approach 

 to languor and yawning which took place as the day 

 advanced, and the almost instant resuscitation of the 

 whole energies of mind and body that ensued on 

 our dismissal, I could not help thinking that, even 

 after making every necessary deduction for the men- 

 tal fatigue of the lessons, and the inaction of body, 

 a great deal of the comparative listlessness and in- 

 difference was owing to the continued inhalation of 

 an air too much vitiated to be able to afford the 

 requisite stimulus to the blodtt, on which last con- 

 dition the efficiency of the brain so essentially de- 

 pends. This became the more probable, on recol- 

 lecting the pleasing excitement occasionally expe- 

 rienced for a few moments, from the rush of fresh 

 air which took place when the door was opened to 

 admit some casual visiter. Indeed, on referring to 

 the symptoms induced by breathing carbonic acid 

 gas or fixed air, it is impossible not to perceive that 

 the headache, languor, and debility consequent on 

 confinement in an ill- ventilated apartment, or in air 

 vitiated by many people, are nothing but minor de- 

 grees of the same process of poisoning which en- 

 sues on immersion in fixed air. Of this latter state, 

 " great heaviness in the head, tingling in the ears, 

 troubled sight, a great inclination to sleep, diminution 

 of strength, and falling down,"'' are stated by Orfila as 

 the chief symptoms,* and every one knows how 

 closely these resemble what is felt in crowded halls. 

 Another instance of the noxious influence of viti- 

 ated air, which made a very strong impression on 

 my mind, was during a three hours' service in a 

 crowded country church, in a warm Sunday in July, 

 The windows were all shut, and in consequence 

 the open door was of little use in purifying the atn 'o- 

 sphere, which was unusually contaminated, not ct Jy 

 by the respiration of so many people, but by ;>.e 



* Toxicologie, il 422. 

 Q2 



