482 RESPIRATION 



great number of noises and sounds, such as barking, neighing, purring, 

 roaring, bellowing, bawling, whining, braying and growling. 



Some of these reactions are voluntary in their nature, others involuntary; 

 furthermore, while some of them are undertaken in consequence of a definite 

 mental concept, others lack a central cause and are reflex in their character. In 

 many cases the latter do not possess a local cause, but are the result of irritations 

 in other parts of the body. Thus, coughing frequently arises from inflammatory 

 reactions in the intestines, stomach, liver, ovaries or uterus, while hiccough is 

 commonly associated with irritations in the stomach, liver or nerve centers. Being 

 reflex in their character, it is possible at times to inhibit these reactions by setting 

 up simultaneous afferent impulses. Sneezing, for example, may be prevented by 

 firmly pressing the finger upon the upper lip, while the act of yawning may be 

 inhibited by a sudden cutaneous stimulus. 



As far as the respiratory movements are concerned, coughing may be defined 

 as an interrupted expiration, the interruption being due to the partial closure of the 

 glottis. But, in order that its purpose may be achieved, which, obviously, is the 

 dislodgment of the irritating body from the respiratory passage, it is necessary 

 to have an adequate supply of air on hand. For this reason, this action is commonly 

 preceded by an inspiration. The air is then ejected through the mouth, the glottis 

 being forced open by the abrupt compression of the intrapulmonic air iri consequence 

 of the contraction of the accessory muscles of expiration. Sneezing is accomplished 

 in practically the same manner. In this particular case, however, the expiratory 

 blast of air is forced through the nasal cavity, the glottis being widely opened, 

 while the cavity of the mouth is shut off from that of the pharynx by the approxi- 

 mation of the base of the tongue to the soft palate. This act is also initiated by a 

 deep inspiration. Sighing is a deep and prolonged inspiration. Brief, jerky 

 inspiratory efforts, made with the mouth closed, constitute the act of sniffing. 

 If the mouth and glottis are kept open, while the vocal cords are thrown into vibra- 

 tion by an expiratory blast which is repeatedly interrupted, the phenomenon of 

 laughing results. Crying is differentiated from laughing by the rhythm of the 

 movement and the position of the facial parts. Sobbing consists of a series of 

 spasmodic inspirations, with partially closed glottis, which are followed by a 

 prolonged expiration. Hiccough is produced by the spasmodic contraction of the 

 diaphragm, the inspiratory motion being suddenly arrested by the closure of the 

 glottis. In yawning a deep inspiration is taken with the mouth and glottis widely 

 open; the succeeding expiration is short. Snoring results if the relaxed uvula 

 and soft palate are thrown into vibration by the inflowing and outflowing air. 



Artificial Respiration. — Conditions arise at times when it becomes 

 necessary to maintain an adequate ventilation of the lungs by arti- 

 ficial means. The methods then commonly practised may be divided 

 into two groups, namely, those devised to expand the lungs from with- 

 out, as in normal breathing, and those effecting their rhythmic in- 

 flation through the trachea by air held under pressure. Artificial 

 respiration is resorted to very frequently during laboratory experi- 

 ments in order to allow us to open the chest without actually destroying 

 the life of the animal. In other cases, it becomes imperative to venti- 

 late the lungs artificially until the cause of the respiratory stoppage 

 has been removed. For example, if an overdose of ether has been 

 given, the prompt employment of artificial respiration generally 

 serves to tide the animal over this period, because in most instances 

 the heart does not cease to act until sometime after the stoppage of 

 respiration. In fact, if this organ has already ceased to beat, it may 



