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PROGRESS OF MICROSCOPICAL SCIENCE. 
Grey Substance of the Cortex of the Cerebrum. — The structure of 
this substance has been quite lately investigated by Prof. Gerlach.* 
He applied the gold method as a hardening means, and found — 
1. That besides the well-known white medullated nerve fibres running 
from the white into the grey substance, and which are arranged in 
fasciculi radiating towards the periphery, there are also numerous 
horizontally-running, medullated fibres, which communicate both 
with one another and with the radially-disposed fibres, forming a 
coarse plexus visible even with a power of sixty diameters. 2. That 
in the meshes of this plexus are contained the ganglion cells, and 
a second far finer plexus of extremely delicate non-medullated fibres 
which can only be brought into view with the highest powers of the 
immersion system. This second plexus is formed of the finest proto- 
plasmatic processes of the nerve cells, whilst the medullated fibres 
appear in part to take their origin in it, the individual fibres becoming 
surrounded by medulla. 3. Some of the protoplasmatic processes of 
the ganglion cells develop directly into medullated fibres without 
branching, and thus such fibres originate partly from the cells them- 
selves, and partly from a plexus of non-medullated fibres. 
Brain Tissue in General Paralysis. — The ‘British Medical Journal’ 
states that at the meeting of the British Medical Association, Dr. J. 
Lockhart Clarke exhibited microscopical sections of brain tissue 
illustrating general paralysis ; and he explained that he had found the 
conditions of brain tissue to be in the first place that of wasting, then 
a widening of the perivascular canals, and a separation of the sheath 
of the same. This sheath (apparently hyaloid) becomes corrugated, 
and contracts round the vessel, which is seen to run within it in a 
tortuous course, the tortuosity often being so great that the vessel 
becomes twisted into knots or kinks. Dr. Clarke further explained 
how he found the white tissue disintegrated, and the grey matter 
wasted ; the grey cells lost their sharp contour ; and their granular 
contents, as a little heap, ready to fall asunder. 
Whence Come Fat-cells ? — This interesting subject has been lately 
taken up abroad, and a very interesting summary of the result is 
given in the ‘ Lancet ’ of August 17. The question of the origin of 
the fat present in every well-nourished person is not easily answered. 
Putting aside the debated point of the direct conversion of the carbo- 
hydrates into fat, there are three theories that have obtained a certain 
amount of credit. The first — resting on the fact that, with free 
supply of oleaginous food, an abundant deposit of fat takes place in 
the subcutaneous connective tissue, in the omentum around the kidneys, 
and elsewhere — maintains that the fat enters the economy in the 
ordinary manner, and is directly stored up in the interior of the fat- 
cells. This view entirely ignores the mechanical and physiological 
difficulty of the passage of an insoluble substance through the cell 
walls. The second view rests on the now well-ascertained fact that 
albumen and its analogues are capable of undergoing disintegration, 
in the course of which, besides other substances, fat is certainly 
* ‘ Centralblatt,’ No. 18. 
