Dr. Wollaston on the salutary Effects of Riding, &c. 11 
from an inclined position, after some degree of previous 
fatigue. Sinking down again immediately removes the giddi- 
ness ; and then, by rising a second time more gradually, the 
same sensation is avoided. 
Part III. On the salutary Effects of Riding , and other Modes oj 
Gestation. 
In the preceding instances of disturbing the circulation of 
the blood, by external motion, the effect is disagreeable, and 
proportionally prejudicial. There may indeed be cases of 
disorder, in which it will be salutary, but these are probably 
less frequent than is generally supposed. 
In the observations which follow, general opinion will 
concur with me, on the benefit derived from external, or pas- 
sive motion, and I hope>, that in ascribing its good effects to 
their true cause, I shall enable others to make a valuable 
distinction, which has not yet been preserved with due care, 
between one motion which is salutary, and another which is 
very frequently pernicious. For, although the term gestation 
is employed by medical writers, as a general term compre- 
hending riding on horseback, or in a carriage, and although 
the merits of such motions, especially the former, were 
clearly noticed, and perhaps even over-rated, by the discern- 
ment of Sydenham, I believe that no explanation has yet been 
given, of the peculiar advantages of external motion, and am 
persuaded, that the benefits to be derived from carria ge 
exercise, are by no means in so high estimation as they ought 
to be. 
Under the common term exercise , active exertion has 
too frequently been confounded with passive gestation, and 
C 2 
