62 THE AMERICAN NATURALIST. [VoL. XXXV. 
The Neurone in Anatomy and Physiology. — The neurone theory 
of the structure of the nervous system as promulgated by Waldeyer 
in 1891 has been subjected to nearly ten years of rigorous criticism, 
and the outcome of this, so far as the present standing of the theory 
is concerned, has been well presented by Professor Verworn,' in his 
address before the Seventy-Second Meeting of the German Natural- 
ists and Physicians. The fundamental postulate of the neurone 
theory, namely, that nerve fibres are processes from ganglion cells 
and that the so-called ganglion cell with these processes constitutes 
the real cellular unit of the nervous system, is clearly stated at the 
outset. The possibly closer union of these units than has heretofore 
been admitted, particularly by the adherents of the contact theory, is 
considered in the light of the recent work by Apathy and by Bethe 
and pronounced still uncertain. The whole issue of this discussion 
is rightly shown to be of secondary importance so far as the stability 
of the neurone theory is concerned. 
From the physiological side the author makes an excellent presen- 
tation of the question as to the significance of ganglion cells. The 
recent arguments of Bethe and of Steinach, to the effect that central 
nervous operations are possible without ganglion cells, are shown 
to be inconclusive, and many important observations made on 
animals subjected to nerve poisons are adduced to show that central 
nervous operations are dependent on ganglion cells for more than 
a supply of nutritive material. The essay concludes with the state- 
ment that the anatomical and physiological investigations of the last 
ten years have left the neurone theory on a firm basis and is unques- 
tionably one of the best recent estimates of the present standing 
of that theory. P 
Avian Helminths. — An important contribution on the frequence 
and distribution of the internal parasites of birds has recently been 
published by Wolffhügel? In all 630 hosts belonging to 73 species 
of birds were examined. Most of them were native in the country 
immediately bordering on the southern Rhine, but a few came from 
the collection of the Basel Zodlogical Garden. In all 180 birds 
proved to be uninfected ; the rest harbored of cestodes 35 species in 
231 hosts, of trematodes 19 species in 124 hosts, of nematodes 26 
species in 252 hosts, and of Acanthocephala 11 species in 41 hosts. 
1 ` 
Verworn, M. Das Neuron in Anatomie und Physiologie. Jena, G. Fischer, 
I 
. 54 pp. 
* Wolffhügel, K. Beitrag. sur Kenntnis der Vogelhelminthen. Dissertation. 
Freiburg, B. 1900. 204 pp., 7 double plates. 
