34 GENEEAL ACTIONS OP DRUGS 



of leucocytes (leucocytosis) occurs in acute diseases accom- 

 panied by a local exudative process, and also in leukaemia, 

 etc. Recent experience with nucleic acid and tallianine 

 (see p. 545) proves that tbey induce leucocytes and are 

 valuable in bacterial infections. Arsenic, and in some cases 

 quinine, appear to reduce the leucocytosis, and in leukaemia 

 seem to thus aid recovery. Drugs altering the consistency 

 of the blood are : Calcium chloride and (to a less extent) 

 other calcium salts, gelatin and potassium iodide, which 

 increase the rate and degree of coagulation ; cod-liver oil, 

 which augments the solids in the blood ; and toxic doses of 

 mercury, which lessen the solids and coagulation and in- 

 crease the fluidity of the blood. 



II. — Drugs Acting on the Heart. 



The mechanism controlling the heart, which is influenced 

 by drugs, is as follows : 



1. Heart-muscle and ganglia. 



2. Inhibitory apparatus, including the vagus nerve roots 

 originating from the medullary centre, and its fibres termi- 

 nating in the heart. 



3. The accelerator apparatus, consisting of the accele- 

 rator nerve — with centres in the cerebrum and medulla — 

 and its fibres passing down the spinal cord to the dorsal 

 nerves ; from thence through the first thoracic ganglion to 

 the sympathetic, and so on to the cardiac plexus, with peri- 

 pheral terminations in the heart. The ganglia in the heart 

 are situated about the auriculo- ventricular groove and at the 

 entrance of the superior and inferior venss cavse, and at the 

 orifices of the pulmonary veins. 



The ganglia have been divided into the inhibitory, 

 connected with the vagus nerve ; the motor ; and the 

 accelerator ganglia ; and they are supposed to be influenced 

 by drugs as well as the rest of the mechanism detailed above. 

 Our knowledge of the functions of these ganglia is imperfect 

 and therefore of the action of drugs on them. 



The action of drugs on the heart-muscle has been deter- 

 mined by estimating their influence on the lower two-thirds 



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