Sneezing: Fallai-iou>i Observations. 189 



of the phenomenon in the following considerations : — On the 

 entrance of an irritating particle into the nose, the [jriniary 

 object of the reflex phenemonon is to increase the flow of 

 mucus, not only for the sake of interposing some non- 

 irritating substance between the sensitive membrane and the 

 foreign pai-ticle, but even more for the purpose of washing it 

 away. This increased flow is produced by a double 

 mechanism. In the first place there is a supply of more 

 blood, and the stimulation of the secreting cells, through 

 nerve influence ; and in the second, there is an increase of 

 vascular pressure from over-fllling of the venous sinuses, as 

 described in Chapter I. Now, this pressure on tiie venous 

 sinuses must be enormously increased by the convulsive 

 respiratory act comprised in sneezing. This latter consists 

 in a violent contraction of the diaphragm, &c., together with 

 the closing of the glottis and the post-nasal space, by 

 contraction of the velum and the superior strictors and of 

 tlie buccal orifice by the approximation of the tongue 

 firmly to the teeth and hai'd palate ; in fact, every possible 

 movement is thrown into action to prevent the exit of air 

 from the larynx, mouth, and nose. What is the immediate 

 consequence of this ? Increase of the intra-thoracic pressure, 

 which necessarily increases the intra-vascular tension, 

 especially in the veins, and hence in the venous sinuses of 

 the nose. The act of forcible expiration, with all the outlets 

 from the thorax closed, if voluntarily induced, i.e., without 

 tlie preliminary irritation in the nose, is scarcely operative 

 in producing the effect described, and it is probably only 

 when the nerve stimulation is excited at the same time, and 

 the gland cells are set working, that this increase in the 

 venous pres.sure is of some additional assistance." 



Reviewing these conflicting statements, we find difference 

 in matters of fact, and necessarily in the inferences drawn 

 from them. Of the inaccuracy of the description of sneezing 

 given in " Foster's Physiology" and the other works referred 

 to, there can be no question. The process seems to be 

 similar to that followed in coughing, with the following 

 amongst other distinctions: — (1) That it is entirely involun- 

 taril3^ (2) That it is caused mainly through stimulation of 

 the anterior portion of the nose. Stimulation of the posterior 

 portion of the nose generally results in coughing. (3) That 

 the forced expiration is, if anything, more mai-ked than in 

 coughing. (4) That the air in persons with normal palate 

 (and apart from voluntarj^ efforts modifying the act) is 



