18 Dr. Golding Bird's Experimental Researches 



gas, and in a few days the same creamy deposit appeared as 

 when exposed to the free air ; lience proving satisfactorily, 

 that the absorption of carbonic acid is not necessary for pro- 

 ducing this curious change. 



4. When simple limpid mucus is boiled in a test tube, no 

 coagulation, as already stated, takes place ; but on prolong- 

 ing the ebullition, a milkiness appears, and after a few minutes 

 an insoluble opake deposit ensues. This change is best ob- 

 served by heating two or three ounces of the mucus over a lamp 

 in a glass basin : the deposit is then more distinct, and by re- 

 pose it becomes considerable. On examination, it is found to 

 consist of albumen in amorphous particles, in which alone it 

 differs from that precipitated from mucus by exposure to the 

 air, or to an atmosphere of hydrogen. This change has been 

 mentioned by Dr. Pearson *, although he did not examine the 

 nature of the deposit. 



5. Another variety of mucous secretion, of frequent occur- 

 rence, is that termed purulent or puriform mucus, secreted 

 copiously during chronic bronchitis. This is generally very 

 opake, often containing greenish masses, exceedingly tena- 

 cious; so that on attempting to pour it from one vessel to 

 another, instead of falling in drops, it forms one continuous 

 rope, sometimes two or three feet in length, which is absolute- 

 ly sectile. It usually contains innumerable air bubbles, which 

 are evolved with difficulty : it can be scarcely said to be mis- 

 cible with water, on account of its excessive tenacity. It bears 

 considerable resemblance to simple mucus concentrated by 

 evaporation, after having deposited part of its combined albu- 

 men by exposure to air. The behaviour of purulent mu- 

 cus with various reagents, therefore, exactly resembles what 

 we should, a priori, expect from operating on simple mucus, 

 holding numerous minute particles of insoluble albumen in in- 

 timate diffusion. In general I have observed all the varieties 

 of mucus to exert a faint but distinct alkaline reaction on sy- 

 rup of violets, and on paper tinted with infusion of rose petals ; 

 and after a few days' exposure to the air this effect becomes 

 still more obvious. Dr. Babington has shown in a late paperf 

 on this subject, that the bronchial mucus is constantly alka- 

 line ; and my friend Mr. Richard Phillips lately informed me 

 that he had been long aware of this circumstance, having de- 

 monstrated it in the saliva by means of cudbear paper. 



6. The globules or particles of insoluble albumen present 

 in puriform mucus are sufficiently obvious under a moderate 



* Philosophical Transactions, 1809, p. 322. 

 t Guy's Hospital Reports, vol. ii. p. 539. 



