53 



of carbon dioxide, more than three times the amount found in the incu- 

 bators, and over four times the amount found in the incubator room. 



The knowledge of this fact led to the belief that possibly a high 

 carbon dioxide content of the air in the incubator chamber during incu- 

 bation was necessary to a successful hatch. The results of analyses so 

 far showed that increased moisture in the incubator gave a decided increase 

 in carbon dioxide, from 9. 15 parts in the dry machines to 10.46 parts in 

 the machines run with moisture, or an increase of 1.31 parts. By refer- 

 ring to Table VII. (page 27) it will be noted that the vitality of the chicks 

 from the hatches was increased from 16. 1 per cent, in the dry machines to 

 32.7 per cent, in the wet machines. 



Four hatches were then conducted, during which a pan of whole 

 milk was kept in each machine. The results of these tests showed that 

 while the carbon dioxide content of the machines was increased from 

 10.46 parts when the machines were supplied with pure water to 12.12 

 when the machines were supplied with whole milk, yet the mortality of 

 the chicks hatched was considerably greater than when pure water alone 

 was used. Buttermilk, however, gave much better results than whole 

 milk, the carbon dioxide content was slightly decreased from 12.12 to 

 12.03 parts in 10,000, while the percentage of chicks alive at four weeks 

 in per cent, of eggs set, was increased from 23.2 per cent, for whole 

 milk and 32.7 per cent, for water to 37.4 per cent, for buttermilk. The 

 increase in carbon dioxide in the machines run with buttermilk and whole 

 milk was due to the emission of this gas during the fermentation of the 

 milk which was inoculated with Bacillus cerogenes lactis before being 

 put in the machine. 



To determine to what extent, if any, these successful hatches with 

 buttermilk were due to the comparatively high carbon dioxide content, 

 machine 3 was fitted up with a gas pipe leading from a drum of artificial 

 carbon dioxide through the fresh air intake to the interior of the machine, 

 where the pipe was so arranged that the gas entering by it would be dis- 

 tributed uniformly throughout' the egg chamber. Approximately 2,500 

 cc. of carbon dioxide was put into this machine twice daily — just after 

 the eggs were turned in the morning and again just after they were turned 

 in the evening. In all, three hatches were made in which artificial carbon 

 dioxide was supplied. Moisture also was supplied during these hatches. 

 The analysis of the air from this machine gave an average of 43.32 parts 

 carbon dioxide in 10,000 of air. The live chicks at four weeks, from these 

 hatches, in per cent, of eggs set, was 37.2, an increase of 4.5 per cent, 

 over moisture only, and about equal to that of buttermilk. The increase 

 in vitality of the chicks from the combination of carbon dioxide and 

 moisture over moisture only, amounting as it does to 4.5 per cent, of the 

 eggs set, seems directly due to the higher carbon dioxide content. At 

 the same time buttermilk used as moisture and a comparatively low car- 

 bon dioxide content gave practically the same result. Again, when the 

 moisture machines were disinfected with zenoleum, the average carbon 



6 Bull. 163. 



