Jury 8, 1915] 
NATURE 507 

Mr. Reid has given me the following additional 
measurements for his specimen :—Girth of neclx in 
front of shoulders 2 ft. 113 in., and girth of chest 
behind shoulders 5 ft. 7 in. 
The okapi has no “hump” at the withers, as might 
be supposed by the length of the spinous processes of 
the dorsal vertebrae and as represented in many 
mounted specimens. The back is as straight as that 
of any horse or antelope. The neck is deep at the 
base and tapers to comparatively small dimensions 
immediately behind the head without any curve. The 
body is rotund, and the limbs remarkably clean and 
sleek. The animal as I have seen it has distinctly 
graceful proportions, and does not give one the impres- 
sion of being all angles as in the giraffe. When stand- 
ing on the alert it holds the neck fairly high, slightly 
above the line of the back, with the head poised at 
an angle, and the ears well forward. 
The animal is probably a surviving primitive form of 
a family closely allied to the ancestors of the giraffes, 
which, as the forest once covering all tropical and 
probably most of subtropical Africa gradually dis- 
appeared by the agency of man, have become modified, 
bulkier animals under the influence of sunlight and 
freedom in the open scrub country, where to browse 
on the young shoots of the thorny acacia trees, grown 
tall and table-topped owing to annually recurring 
grass fires, has necessitated the development of a 
longer neck. 
The giraffe, now restricted to Africa, at one time, 
during the latter portion of the Tertiary period, | 
think, roamed far and wide over southern Europe 
and throughout a large extent of Asia. Similarly the 
okapi’s area of distribution before the destruction of 
the forest was probably much wider than at present. 
There is, in fact, evidence that it inhabited the once 
forest-covered regions of the Upper Nile Valley. 
It was pointed out in 1902 that among the twelfth- 
dynasty paintings from Beni-Hasan, Egypt, 
exists a picture, long known to archeologists, which 
portrays a creature termed ‘‘Sche,” said to have a 
resemblance to the present-day okapi, except that the 
upper lip is somewhat protruded and proboscis-like, 
and there are no zebra-like markings, the body and 
limbs being of a uniformly reddish colour. It is pos- 
sible that this picture represents a form of the olxapi 
known to the ancient Egyptians. C. Curisty. 
July 5. 




Testing Respirators. 
Tue chief difficulty in the determination of the rela- 
tive efficiency of these safeguards which are so freely 
offered to the public, and also utilised for the purposes 
of war, is the want of a standard method of testing 
the same. 
As the result of a few preliminary experiments, I 
would suggest in the testing of different fabrics 
impregnated with chemical substances that the condi- 
tions of working must be standardised, and the 
following conditions met. A suitable container for the 
mixture of air and the poisonous gas is required, and 
this must lead directly to the surface of the fabric 
which is exposed to the action of the mixed gases as 
they pass through its substance. 
The rate of flow of the gas through the cloth must 
slightly exceed that of the inflow of air under actual 
breathing conditions, and this must be standardised. 
The reduction in the amount of the added gas is 
observed by actual analysis, and the test only made 
after the air has been passing for a stated period, 
which must not be less than five minutes. The com- 
position of the air being tested must correspond with 
NO. 2384, VOL. 95] 

there’ 
that likely to be met with in practice. In the case of 
chlorine the reduction in the amount present in the 
air passing the treated screen can be easily observed 
by actual estimation. As so much depends upon the 
amount of moisture present on the screen, this should 
be also standardised. It may be contained in the gas 
as it passes the screen, which must be of constant 
area. 
It is only possible by such means to study the effect 
of varying moisture on the rate of absorption, etc., 
and to set up standard conditions which will enable 
comparative results to be obtained. 
I hope soon to be able to suggest what these 
standard conditions should be, and the best type of 
apparatus necessary to carry out comparative experi- 
ments. W. P. DREAPER. 
London, E. 

vere d falhiz i 
Photograph of Mellish’s Gomet. 
I ENcLOsSE herewith a contact print from a negative 
of comet Mellish obtained with the Franklin Adams 
star camera of the Union Observatory on June 6, 1915, 
with an exposure of ninety minutes. The position of 

Comet Mellish, June 6, 1915- 
Exposure, gom. 
the comet was then R.A. 22h. 35m., declination 70° 18 
south. 
The proximity of the comet to the pole is well 
shown, even over the small region of the photograph, 
by the change in the direction of the star trails. 
. H. E. Woop 
(Chief Assistant). 
Union Observatory, Johannesburg, June ro. 
