Class III. 1. 1. i: OF VOLITION. 291 



remove the caufe of the difeafe, are not properly convulsions, 

 but exertions immediately caufed by fenfation ; but in this kind 

 of afthma they are only efforts to relieve pain, and are frequent- 

 ly preceded by other epileptic convulfions. 



Thefe two kinds of afthma have fo many refembling features, 

 and are fo frequently intermixed, that it often requires great at- 

 tention to diftinguifh them ; but as one of them is allied to ana- 

 farca, and the other to epilepfy, we mail acquire a clearer idea 

 of them by comparing them with thofe diforders. A criterion 

 of the humoral or hydropic afthma is, that it is relieved by copi- 

 ous fweats about the head and breaft, which are to be aicribed 

 to the fenfitive exertions of the pulmonary veffels to relieve the 

 pain occafioned by the anafarcous congeftion in the air-cells ; 

 and which is effected by the increafed abforption of the mucus, 

 and its elimination by the retrograde action of thofe lymphatics 

 of the fkin, the branches of which communicate with the pul- 

 monary ones ; and which partial fweats do not eafily admit of 

 any other explanation. See Oafs I. 3. 2. 8. Another criterion 

 of it is, that it is generally attended with fwelled legs, or other 

 fymptoms of anafarca. A criterion of the convulfive afthma 

 may be had from the abfence of thefe cold clammy fweats of the 

 upper part of the body only, and from the patient having ccca- 

 fionally been fubject to convulfions of the limbs, as in the com- 

 mon epilepfy. 



It may thus frequently happen, that in the humoral afthma 

 fome exertions of the lungs may occur, which may not contrib- 

 ute to difcharge the anafarcous lymph, but may be efforts limply 

 to relieve pain ; befides thofe efforts, which produce the increas- 

 ed abforption and elimination of it ; and thus we have a bodily 

 difeafe refembling in this circumftance the reverie, in which 

 both fenfitive and voluntary motions are at the fame time, or in 

 fucceihon, excited for the purpofe of relieving pain. 



It may like wife fometimes happen, that the difagreeable fen- 

 fation, occafioned by the congeftion of lymph in the air-cells in 

 the humoral or hydropic afthma, may induce voluntary convul- 

 fions of the refpiratory organs only to relieve the pain, without 

 any fenfitive actions of the pulmonary abforbents to abiorb and 

 eliminate the congeftion of ferous fluid ; and thus the fame 

 caufe may occafionally induce either the humoral or convulfive 

 afthma. 



The humoral afthma has but one remote caufe, which is the 

 totpor of the pulmonary veffels, like that which occurs on going 

 into the cold bath j or the want of abforption of the pulmonary 

 lymphatics to take up the lymph effufed into the air-cells. 

 Whereas the convulfive afthma, like other convulfions, or epi- 

 leptics, 



