1 10 ELEMENTARY BIOLOGY 



141. Taste of food. On looking over a bill of fare the dif- 

 ferent persons in a party are likely to make different selections. 

 And in marketing for the family the mother or housekeeper 

 will usually order a great variety of food articles. The reason 

 for this is that " tastes differ/' It is an important practical ques- 

 tion to consider whether people should indulge their tastes, and 

 especially whether children should be allowed to eat what they like. 



We have been told (p. 89) that it is not wise to depend 

 altogether upon instinct as a guide in the selection of the 

 kinds and in the determination of the amounts of food eaten. 

 And yet we cannot ignore instinct and taste entirely. In the 

 first place, food that is not agreeable to the taste will be of 

 very slight value to a person. Experiments made originally 

 by the great Russian physiologist, Professor Pawlow, 1 and since 

 repeated and extended by others, showed that the secretion 

 of digestive juices in higher animals depends upon the stimu- 

 lation of nerves connected with the tongue and throat. We 

 have all had the experience of the " mouth watering " when 

 some attractive food is smelled. Stated in other words, this 

 means that when certain nerves are stimulated (in the nasal 

 lining and in the palate), the salivary glands begin to pour 

 forth their special product. Now it is only when these same 

 and certain other nerves are sufficiently stimulated that the 

 stomach begins to water, that is, to pour forth the gastric 

 juices from the glands into the stomach cavity. 



Gastric juice will digest proteins, in the stomach or in a 

 teacup, without regard to anyone's feelings. Saliva will digest 

 starch, in the mouth or in a tin can, without regard to 

 anyone's feelings. But the glands of the stomach and the 

 glands of the mouth will produce and secrete juices more 

 readily when the palate is pleasantly stimulated than when 

 it is not stimulated. Indeed, under certain conditions the 

 glands of the stomach will not secrete digestive juices at 

 all, although there may be a great quantity of food in the 



1 Pronounced pav'lof. 



