TOXICOLOGY. 359 



In articular rheumatism, the character of the local 

 swellings and the tendency to metastasis, as well as 

 the acute pain and its persistence, are diagnostic symp- 

 toms. 



Morbid Anatomy. — In Acute Cases, the muscles are found 

 both in a softened and blanched condition. The lungs and 

 trachea are often inflamed. The mucous membrane of the 

 alimentary tract shows alteration of structure, and is some- 

 times softened and pulpy over a considerable area, owing to 

 infiltration into sub-mucous layer. 



Sometimes in parts there are blood extravasations of 

 variable size and extent. The muscular tissue of the heart 

 is softened and flaccid. 



Ecchymosis under the endocardium is not present, 

 whereas in acute arsenical poisoning, it is, we believe, almost 

 invariably found after death. 



The membranes of the brain are often congested. 



In Chronic Cases the mucous membranes of the intestines 

 and stomach present patches of ecchymosis and the caecum 

 and colon often show gangrenous patches. 



The swellings in connection with the joints are com- 

 posed of a collection of clear fluid outside the joint 

 cavity. 



Method of Defection of Lead. — The presence of lead in 

 solution may be demonstrated by : 



(1.) On passing sulphuretted hydrogen through it, or on 

 adding a few drops of sulphide of ammonium, a black 

 precipitate is formed. 



(2.) A white precipitate results from the addition of 

 liquor potassse or liquor ammonite. 



(3.) Dilute sulphuric acid gives a similar precipitate, which 

 is insoluble in nitric acid. 



(4.) Iodide of potassium gives a bright- yellow deposit 

 (iodide of lead). 



