444 THE LAWS OF ORGANIC 



because the quality or character of the secretion 

 is, in the same manner, altered ; and, whenever 

 this effect occurs, the membrane becomes less ad- 

 herent to the internal surface of the trachea, be- 

 cause the diseased matter which connected the two 

 is displaced by what is healthy. Vomiting may 

 sometimes be the cause of removing this, by the 

 agitation which attends its operation ; and it will 

 materially facilitate this result, if the mucous 

 membrane to which it is attached has experi- 

 enced the more extensive and previous influence 

 of those agents that regulate the secretions by im- 

 proving the qualities or distribution of the blood. 

 DXLII. The mode in which the secretory 

 functions are acted upon by vomiting, is not, on 

 all occasions, easy to explain. The following 

 reasons, which are assigned, may probably be 

 considered to make an approach towards a cor- 

 rect explanation : Inflammation is never absent 

 in croup ; indeed, this is the nature of the dis- 

 ease ; and, whenever any part of the body be- 

 comes the seat of inflammation, it is always ac- 

 companied by an increased action, or congested 

 condition of the blood-vessels. The increased 

 action probably depends on an increased quantity 

 of blood which these receive, this also being of a 

 more stimulating description than usual ; and the 

 congestion may happen when the vessels are not 

 enabled to circulate the blood transmitted to them, 

 this, on the other hand, being of a less stimulating 



