254 NOTES AND MEMORANDA. 



which under the microscope proved to be myelin (colloid? Hep.). 

 These masses were often foimd lying detached on the surface of the 

 section, and presented a greenish lustre. The author states that he 

 has seen the same in the spinal cord of a horse that had suffered from 

 rheumatic tetanus, and that he had regarded it as a softening and 

 chemical alteration of the substance of the spinal cord. 



The signs of inflammation are not presented everywhere in the pia 

 mater, but only in certain parts. The distribution of these in the 

 grey matter and in the central white substance throws a new light, 

 according to Dr. Bonedikt, ujion the nature of the " granular disinte- 

 gration." (A diagram intended to illustrate this point is given.) From 

 what he has noted, it is concluded that the j)athological process in 

 this disease consists in acute exudative inflammation, with hyaloid 

 degeneration, which doubtless arises from the exudative infiltration of 

 the connective tissue. It is characteristic with reference to these 

 inflammatory products that the attack, in man at least, is ushered in 

 with rigors. The hyperemia and nuclear proliferation is concurrent 

 with that form of diffused inflammation which Lockhart Clarke has 

 designated as " granular disintegration," and so far, the author con- 

 siders, the anatomical obscurity of this disease is disjielled. The 

 morbid process, in man, is doubtless essentially the same. The usual 

 post mortem appearance is congestion and softening, which may have 

 no especial value except as following asphyxia. 



Dr. Benedikt states that there are in literature only two trustworthy 

 reports, viz. by Meynert, who found much the same appearances as the 

 author. The spaces, or holes, are regarded by Meynert as being the 

 result of the hardening of the brain-substance. In two other cases 

 Meynert found hypertroj^hy of the connective tissue in the posterior 

 columns, with molecular and amyloid degeneration in the anterior 

 columns. The nerve-cells of the cortical matter had also undergone 

 jiartly molecular and partly sclerotic change. 



NOTES AND MEMOEANDA. 



The Method of Measuring Angular Aperture.— The 'American 

 Naturalist ' (August) states that Mr. Wcnham, in order to gain accu- 

 racy in measuring the angular aperture of dry objectives, would like 

 to cut off all stray light that might enter the lens without being 

 callable of forming an image, by placing over the objective a conical 

 nozzle having a small aperture in its apex. This aperture would 

 correspond to the focus of the lens, and the nozzle would just include 

 the cone of rays capable of forming an image, and would exclude all 

 false rays of any considerable angle. This method would be inconve- 

 nient, however, and as the angle is measured by a horizontal move- 

 ment, a vertical slit will be a satisfactory substitute. For high powers 

 the slit must have thin edges ; and it must be caj)ablc of adjustment 

 to the width of focus of the lens. His arrangement is easily made and 



