1 76 DWIGHT ELMER MINNICH. 



the period of water diet was ended and a period of iM saccharose 

 diet begun. During this period each animal was subjected to 

 five trials with water, each trial being followed, in case of no 

 response, by a trial with saccharose. These experiments, there- 

 fore, furnish data on the response of animals which were o per 

 cent, responsive to water, to iM saccharose during periods of 

 water diet and iM saccharose diet. 



The data from these experiments are to be found in Table IV. 

 Both Phormia and Lucilia were employed, the results for the two 

 species being strikingly similar. Phormias which had been 

 rendered unresponsive to water by administration of the same, 

 remained 93 per cent, responsive to iM saccharose, while 

 Lucilias under the same conditions remained 96 per cent, respon- 

 sive. When the diet was changed from distilled water to iM 

 saccharose, the response to water continued to be zero or nearly 

 so, and the response to iM saccharose, though somewhat di- 

 minished, continued to remain high: 82 per cent, in the case of 

 Phormia; 80 per cent, in the case of Lucilia. Thus, the adminis- 

 tration of water failed to reduce the response to saccharose 

 appreciably, while the administration of saccharose reduced it 

 somewhat. 



Differences were noted not only in the numbers of responses 

 under the various conditions described, but in the character of 

 responses as well. In general, during water diet, the response to 

 iM saccharose was much more vigorous than the response to 

 water. The slightest contact of the tarsi with the sugar solution 

 often caused the proboscis to be extended violently and to remain 

 so until the solution was washed off. Corresponding to the 

 diminution in the number of responses to saccharose during 

 saccharose diet, there was also some lessening in the violence of 

 the reaction. It is quite clear, therefore, that the contact 

 chemoreceptors of the tarsi distinguish readily between water 

 and a iM saccharose solution. 



It has been previously stated that when tarsal stimulation 

 with a sugar solution failed to elicit a response, contact of the 

 oral lobes at the tip of the proboscis with the solution still proved 

 an effective stimulus. There are, therefore, present on the oral 

 lobes contact chemoreceptors, serving as organs of taste, which 

 are even more sensitive than the organs of the tarsi. 



