112 THE CELL 



cells may undergo greater or less changes in their structure and 

 vital properties. When such changes are apparent to us, we 

 speak of the effects of chemical stimulation. These phenomena, which 

 are so exceedingly numerous, may vary considerably, according as to 

 ivhether the whole, or only part, of the cell-body is affected by the 

 stimulus. 



a. First group of experiments. Chemical stimuli which 

 affect the whole of the body. In order to throw light upon 

 this first group of phenomena, the behaviour of protoplasm towards 

 certain gases, which are grouped under the common name of 

 anaesthetics, must be investigated. 



The protoplasmic movements of a plant cell soon become 

 arrested, if, instead of being put into water, it is placed in a drop 

 of olive oil, by which means the air is excluded (IV. 15). After 

 the oil has been removed, the movements are seen to gradually 

 recommence. 



The streaming movements may in a similar manner be slackened 

 and finally completely stopped, if the air is replaced by carbon di- 

 oxide or hydrogen. For these experiments special slides with gas v 

 chambers have been constructed through which a current of 

 carbon dioxide or hydrogen may be conducted. If the plant 

 cell is kept from 45 minutes to an hour in a current of carbon 

 dioxide, the movements are as a rule completely stopped ; when 

 hydrogen is used, a longer time must be allowed (III. 5). This 

 protoplasmic paralysis may, if it has not been allowed to last too 

 long, be removed by the addition of oxygen. "Apparently living 

 protoplasm unites chemically with the oxygen of its environment. 

 The definite oxygenated compound thus produced, of which under 

 ordinary conditions a considerable amount must be assumed to 

 exist in every protoplasmic body, is continually broken down 

 during the movements, whilst carbon dioxide is probably given 

 off" (Engelmann III. 5). Hence the removal of oxygen has a 

 paralysing effect upon the irritability, and indeed upon all the 

 vital activities of the protoplasm. 



Such anaesthetics, as chloroform, morphia, chloral-hydrate, etc., 

 have a marked influence upon the vital activities of the cell. 

 These substances do not affect the nervous system alone, as is 

 frequently believed, but all the protoplasm of the body. The 

 difference is only a matter of degree ; the irritability of the 

 nerve-cells is more quickly lowered and finally destroyed than 

 that of the protoplasm of other cells. Further, when narcotics 



