Cigaret smoke 3.75 to 84 per cent. Pipe mixture smoke, smoked as cigarets 79 " " Pipe smoke 77 to 92 " " Cigar smoke 31 to 63 " " The United States Department of Agriculture[43] found in tobacco smoke about 30 per cent. of the nicotin originally present in the tobacco. Contrary to general opinion, Havana cigars contain less nicotin than the cheaper brands, which augurs ill for the large class of people who cannot afford to smoke higher priced brands. Many of the cheaper grades do, however, show a low percentage of nicotin. [Sidenote: Effects on Animals and Man] By means of an ingenious apparatus, Zhebrovski,[44] a Russian investigator, compelled rabbits to smoke cigaret tobacco for a period of 6 to 8 hours daily. Some died within a month, and showed changes in the nerve-ganglia of the heart. Others established a tolerance similar to that exhibited by habitual smokers, but upon being killed at the end of five months, degenerative changes similar to those produced by the injection of nicotin were found, viz., hardening of the blood vessels. There is, indeed, no difficulty in producing the characteristic effects of nicotin by administering tobacco smoke, either in man or in animals.[45] Nicotin causes brief stimulation of brain and spinal cord, followed by depression. There is an increased flow of saliva, followed by a decrease (large doses diminish it at once) and often nausea, vomiting and diarrhea. The heart action is at first slowed and the blood pressure increased. Subsequently there is a depression of the circulation, with rapid heart action and lowered blood pressure. In habitual smokers, this preliminary stimulation may not occur. The stimulating effect on the brain is so brief that tobacco can not properly be termed a stimulant. Its effect is narcotic or deadening. Those who fancy that their thoughts flow more readily under the use of tobacco are in the same case with any other habitué whose thoughts can not flow serenely except under his accustomed indulgence. That a sound healthy man, who has never been accustomed to the use of tobacco, can do better mental or physical work with tobacco than without it has never been shown. Indeed, such experiments as have been made on students and others show to the contrary.[46] The statistics presented by Prof. Fred. J. Pack are of interest in this connection. In six educational institutions the students competing for places on the football team were grouped as follows: