26 FORESTS, WOODS, AND TREES 
media containing minute particles of carbon. Turpentine 
and allied substances, used in minute quantities as media, 
greatly increase the number of carbon particles that are 
swallowed by the leucocytes. In a dilution of 1: 100,000 
an increase was found of 24:7 per cent. In the presence 
of turpentine the percentage of the white cells that have 
taken in carbon is greater than in the case where no 
turpentine is added. This explains the remedial action of 
a subcutaneous injection of turpentine in the treatment of 
pneumonia in horses, as minute quantities of the turpentine, 
dissolving in the lymph of the tissue spaces and afterwards 
entering the blood circulation, promote the phagocytic 
power of the white corpuscles in the lung. 
Hamburger says that the cause of the remarkable in- 
fluence of a sojourn in high mountain regions on metabolism, 
on sleep, and on the state of the mind is entirely unknown. 
It has been proved that these phenomena are not due to the 
altitude as such, for in balloons they do not occur, nor are 
they found in all mountain regions, but only in those parts 
with coniferous woods. He thinks that it is due to the 
stimulating action of the odour of resin, turpentine, etc., on 
the nerve cells. The exhalations of the trees reach the 
lungs by inspiration, and are transported by the blood 
current through the whole body, and in consequence to the 
nerve cells, thus promoting metabolism, sleep, ete. May 
not such vapours, however, brought directly into contact with 
the white blood corpuscles in the lungs by every breath 
taken in, stimulate these to vigorous attacks on the tuber- 
culosis bacteria ? 
It is probable then that Pliny was right in his view of 
the curative influence of pine forests; but at the same time 
we must not forget the injurious effect of screens of trees 
and shrubs close to a dwelling in blocking out sunshine 
and in stagnating the air. 
As forestry work, varied in character and in muscular 
effort, can be carried on out-of-doors in all seasons, it is now 
utilised in the sanatorium treatment of consumptive patients. 
This is one of the features of the interesting afforestation 
