REFLEXES 103 



ously whatever is put between its lips. In the natural 

 course of events this reaction, joined with swallowing, in- 

 sures a supply of food. As it eats it frequently chokes and 

 coughs; the cough is a reflex which prevents the entrance of 

 foreign materials into the breathing passages. A similar 

 reflex sneezing is calculated to expel obstructing sub- 

 stances from the nose. Vomiting is a reflex which relieves 

 the overfilled stomach. Crying has a less obvious function 

 unless we assume that it secures the attention of the 

 parents to needs which the child by itself cannot satisfy. 



Some of the reflexes which are prominent in the baby 

 are disguised or repfaced by others during the period of 

 growth. Sucking ceases to be a predictable perform- 

 ance. Crying is less and less readily induced. The 

 other responses which we have mentioned continue to 

 occur. So, too, the reactions of the pupils and the 

 withdrawal of parts of the body from objects that 

 threaten injury are retained. In the course of a year 

 or two the child has the capacity to keep its feet and to 

 walk, attainments based largely upon the development 

 of reflex mechanisms. 



Reflexes Other than Movements. So far we have 

 spoken of reflexes as though they were necessarily 

 acts of the muscles. The conception must now be 

 made broader. Certain reflexes have a negative or 

 inhibitory character. A dash of cold water may cause 

 one to hold the breath momentarily and perhaps at the 

 same time the heart may " drop a beat." The suspension 

 of breathing and the omission of the heart's contraction 

 are true reflexes, but instead of being movements they 

 consist in the suppression of movements which were 

 due to occur. 



There are also reflexes which are executed by glands 

 instead of muscles. A gland is an organ which pre- 

 pares and discharges some chemical product. Either 

 the action of the gland or its product may be described 

 by the word secretion. Some glands, like the kidneys 

 and the liver, continuously evolve their secretion; others 



