ZOOLOGY AND BOTANY, .MICROSCOPY, ETC. I i 5 



Zinc chloride solution gives the following reactions : Cotton, linen 

 and hemp, claret-red ; wood, straw, esparto and jute cellulose, partly 

 blue, partly reddish and blueish violet ; manila hemp, blue, blucish 

 violet, dull yellow and greenish yellow ; wood pulp and raw jute, lemon 

 ■to dark yellow. Before applying zinc chloride solution, the pulp must 

 be freed from water by squeezing it on a porous plate. The fibres 

 are then teased out with platinum needles and covered with a thin 

 •cover-glass. 



The structural characters of the different fibres when inspected under 

 the Microscope are as follows. Cotton fibres appear as flat ribands, 

 usually twisted on themselves. The flax fibre is round and fairly 

 regular, and shows a narrow central canal with numerous dark cross- 

 lines, and the characteristic linen bulbs. Hemp fibres cannot be dis- 

 tinguished from flax fibres. Mechanical wood has a ragged or torn 

 appearance, and its structure is not fibrous. It also shows pitted vessels 

 or pores and cross-markings on many of the cells. The bast fibres of 

 jute are distinguished by a canal, the width of which varies considerably. 

 Wood cellulose fibres are usually flat, often twisted, and not unlike 

 cotton ; not infrequently pitted pores are visible. Straw fibres are 

 round and smooth, and accompanied by numerous cuticular cells, some 

 of which are very wide and flat, whilst others are peculiarly marked and 

 serrated. The spiral-shaped cells carry a ring at each end. Esparto 

 fibres and cells are very similar in appearance to straw fibres and cells. 

 The characteristic pear-shaped hairs or cells are, however, always present, 

 and afford a ready means of distinguishing esparto from grass. 



Detection of Trypanosomes.* — As Trypanosomes are not present 

 in large numbers it is necessary, says A. Castellani, to draw off at least 

 15 c.cm. of cerebrospinal fluid. It is better to reject the first few cubic 

 centimetres as they are apt to contain blood. When the fluid comes away 

 • clear, 10 c.cm. are collected and centrifuged for 15 minutes. The deposit 

 is slight. The sediment, which is whitish, is examined under a mode- 

 rately low power, and as the trypanosomes are at. first fairly active they 

 are easily detected. 



D. Bruce and D. Nabarro adopt the same method as the foregoing 

 for examining the cerebrospinal fluid obtained by lumbar puncture. In 

 the case of blood, they found that the presence of the corpuscles was a 

 barrier to detecting the parasites, and it is a curious fact that both 

 filarise and trypanosomes resist the centrifugal action, and arc most 

 readily found after being centrifuged three or even four times. The 

 procedure adopted was to collect 10 c.cm. of blood from a vein, in 

 a test-tube containing a little citrate of potash solution to prevent 

 coagulation. After centrifuging for- 10 minutes the clear layer was 

 poured off and again centrifuged, and this procedure was repeated four 

 times, the sediment from each centrifuging being examined micro- 

 scopically. 



Method for the Investigation of Fossils by Serial Sections.t 

 W. J. Hollas points out that the mechanical difficulties which preclude 



* Roy. Soc. Rep. Sleeping Sickness Com., No. 1 (1903) 88 pp. (10 pis.). 

 + Proe. Roy. Soc, lxxii. (1903) p. 98. 



