438 SECTIONAL TRANSACTIONS.—J. 
curve fitting, a rough indication may be had of how far back in the preceding 
stroke the change in muscle action took place. 
Another peculiarity of non-reciprocating strokes is that the initial rate of 
motion which can be voluntarily given a limb starting from rest is greater the 
greater the load up to a certain limit, after which the initial possible rate 
decreases to the point of immobility. This feature seems to vary in some 
degree with the conscious factor (a) whether the subject has or has not know- 
ledge of the load to which he is to be subjected; (b) the degree of muscle 
tension he maintains when awaiting the signal to stroke. 
(c) Dr. C. 8S. Myzrs, C.B.E., F.R.S.—Conceptions of Fatigue. 
Fatigue may arise from the exhaustion of the material stored up by living 
sukstance for the manifestation of its specific activity (contraction, heat seusa- 
tion, &c.) or from the accumulation of the waste products of such activity. 
This kind of fatigue occurs usually after powerful spasmodic acts; and at 
present, at least, it is to be distinguished from the fatizue affecting the con- 
tinuous set of control or direction, which results in posture and in orderliness 
of acts. Two kinds of set may be usefully recognised : ‘ Extrinsic set’ involves 
“inhibition of unfavourable or incompatible acts or sets; it preserves a faveur- 
able ‘attitude’ (mental or motor). ‘ Intrinsic set’ involves poise between 
antagonistic acts; in muscle it is manifest as protracted tone or posture, and 
visual and thermal sensibility as adaptation to colour (or brightness) and tem- 
perature. Adaptation is thus a state of posture, not a state of fatigue. 
‘Throughout mental and muscular activity, direction and the elaboration of 
material for acts concur, posture and attitude being the matrix in which 
acts occur, the former engaged rather in elevating, the latter in degrading 
energy. in everyday life, the former kind of fatigue is of far greater import- 
ance than the latter. On it depend the acquisition, preservation, and manifesta- 
tion of skill, attitudes of attention, &c.; but of its nature we are ignorant. 
(d) Prof. F. 8. Lzz.—Physiological Aspects of Efficiency in Industry. 
10. Presidential Address by Prof. W. McDoveatt, F.R.S., on 
Purposive Striving as a Fundamental Category of Psychology. 
(Page 226.) 
11. Dr. Morton Prince.—The Problem of Personality. 
12. Wing-Commander E. C. CLtements.—Binocular Vision and Correct 
Ocular Muscle Balance: its importance in everyday life. 
From the experience of clinical practice and special experiments the author 
has formed the opinion that binocular vision with correct ocular muscle balance 
is necessary (1) for the correct mental interpretation of impulses received, and 
(2) for efficient muscular co-ordinative response thereto. Lack of the above 
requirements has been found in many cases to account for (1) inability to 
land aeroplanes; (2) lack of manual dexterity or clumsiness at certain occupa- 
tions ; (3) lack of skill at games requiring ‘eye’; (4) loss of efficiency of per- 
formance in acts such as above due to fatigue, illness, or other causes. In 
many cases by special visual training exercises the defects can be removed and 
correct performance of the various acts ensured. 
13, Prof. E. A. Borr and Mr. 8. F. N. Cuanrt.—A New Method of 
Stereoscopy, with Applications to Motion Pictures. 
The discoveries of Wheatstone and Brewster in stereoscopy attracted world- 
wide attention in the middle of the nineteenth century. This interest as quickly 
died out because no result of scientific importance nor any useful application 
was at that time found for this remarkable visual phenomenon, and in conse- 
quence the stereoscope became little more than a household toy. Later in the 
century interest was revived in some circles through the use of certain charac- 
teristics of stereoscopic fusion in the detecting of forgeries and counterfeits, the 
matching of pattern materials, the surveying of inaccessible regions, astro- 
