NOTES AND MEMORANDA. 71 



cliaractei', is exemplified in the ' Loodiana fever,' which has been so 

 fatal to horses in the East. The dried blood of horses that had died 

 of this disease in India has been recently sent to the Brown Institu- 

 tion, and there afforded seed from which a crop of Bacillus anthracis 

 has been grown, which justified its distant pathological origin by 

 reproducing the disease in other animals. Other equally interesting 

 experiments have been made at the same Institution, showing that the 

 * grains ' which are so largely used as food for cattle, aff'ord a soil 

 which is peculiarly favourable for the development and growth of the 

 spore filaments of Bacillus ; and that by such ' grains ' when in- 

 spected, the anthrax fever can be produced at will, under conditions so 

 simple, that they must often arise accidentally. The bearing of this 

 fact on a recent instance in which anthrax suddenly broke out in a 

 previously uninfected district, destroying a large number of animals, 

 all of which had been fed with grains obtained from a particular 

 brewery, need scarcely be indicated." * 



Method of representing an Object from Microscopic Sections. — 

 Whilst working on the central nerve system of the crayfish, Herr 

 Krieger, of Leipzig, adopted the following method of obtaining as 

 clear a view as possible of the internal structure. 



The ganglia, after being hardened and stained, were imbedded in 

 paraffin, and cut by the microtome into a series of transverse sections. 

 For every section the position of the object-slider was read oft' on the 

 scale of the microtome. When a satisfactory series of sections had 

 been made, they were drawn with a camera, and the difterent tissue- 

 elements (ganglia-cells, nerve-fibres, &c.) were marked out with 

 difterent colours. Then a millimetre scale was drawn with the same 

 amplification, and a sheet of paper ruled with parallel lines whose 

 distance aj)art, according to this scale, was equal to the tliickness of 

 the sections. Each of the drawings was then orthograi^hically pro- 

 jected on to a straight line drawn parallel to the transverse axis of the 

 section, and, when the direction of the cut was exactly at right 

 angles to the longitudinal axis of the object, each projection, according 

 to its place as determined by the readings of the microtome scale, 

 was marked off' between the parallel lines in such a manner that the 

 middle points of the projection (symmetrical on both sides) fell on a 

 straight line drawn at right angles to the parallel lines. Nothing 

 more has now to be done but to connect together the points of the 

 projections corresponding to the outlines of the various structures, 

 and by slight shading, &c., to distinguish between those lying higher 

 or deeper, in order to get a representation of what the object would 

 look like if it were perfectly transparent and were viewed from above. 

 If the direction of the cut is not exactly at right angles to the 

 longitudinal axis of the object, we must determine, by comparing 

 the unsymmetrical halves of the section with those of the preceding 

 and following ones, the angle of the symmetrical plane to that of 

 the direction of the cut — draw the central line so that it forms this 

 angle with the parallel lines, and mark off the projections as before. 



♦ ' Proc. Roy. Soc.,' vol. xxviii. p. 43. 



