412 
stimulate, and, if too intense, retard its growth, and 
ultimately destroy the molecular structure required 
for mitosis. In:so far the effects on the growth of the 
cell—superficially, at least—resemble those on the 
formation of the latent image. 
It is also found—and, as already stated, the whole 
efficacy of radio-active treatment turns upon this— 
that in the case of the pathological cell these pheno- 
mena appear all in advance of the like effect in the 
normal cell. There exist then states of the cell differ- 
ing in sensitiveness towards radiation just as there 
exist differing states of the film. 
The accelerated mitosis and growth of the patho- 
logical cell appear in some cases to be traceable to 
repeated mechanical stimuli. This is parallel with the 
formation of the latent image by similar stimuli. 
Finally, the destruction of the pathological cell is 
said to be brought about by thermal radiation of a 
certain intensity. A method of treatment has even 
been founded on this. The parallel with the latent 
image also appears here. 
There is, then, a very complete parallel between the 
effects of radiative and mechanical stimuli in both 
cases, the latent image and the cell. The formation 
of both may be promoted by radiation, and by the 
same radiation in excess may be finally destroyed. 
It seems permissible to ask if the same parallel does 
not extend to more definitely chemical effects. The 
point is important, not only on the score of the con- 
venience and accessibility of the plate as a means of 
investigation, but because of certain conclusions which 
can be drawn from already known data, and which 
possibly possess a bearing on what is termed the 
cancer problem. 
We may state the argument thus :—We find certain 
chemicals producing in the film what are to all appear- 
ance identical effects with those generated in it by 
radiation. And reasoning from the fact that radiation 
produces parallel results in the case of the cell and 
the film, we ask if those chemicals which affect the 
latent image in the direction of acceleration or re- 
tardation may not also in like manner affect the cell. 
The view that this question is legitimate is supported 
by some observational facts, as will presently appear. 
But first it is necessary to look more closely at what 
may be really involved in comparing the formation 
of the latent image with the growth of the cell. If, 
at any stage of its metabolism, a partial (or complete) 
reducing action takes place in the cell in which the 
halogen and the colloid present take a part, the simi- 
larity between the two results may be more than a 
parallel. i 
physically identical, or practically so. There may, in 
fact, exist, as a stage in the life of the cell, relations 
between the negative halogen jon, a positive ion united 
with this, and the protoplasm, similar to that prevail- 
ing among the elements of the film. If such exist, 
the explanation of the resemblance in the response 
of the two systems towards different agents, physical 
and chemical, is at once forthcoming. We are not in 
this case involved in the statement that the growth 
of the cell and of the latent image are parallel actions 
beyond the inference that a certain molecular re- 
arrangement necessary for the growth of the cell is 
similar in character to what is presented to our study 
in the formation of the latent image. In a sense the 
formation of the latent image is katabolic, that of the 
cell is anabolic. We are not, however, forcing a com- 
plete comparison between them, nor do the observa- 
tional facts call upon us to do more than recognise 
some photo-sensitive molecular process involved in cell- 
growth similar to one involved in the formation of 
the latent image. 
There seems to be no doubt that the growth of the 
NO. 2380, VOL. 95] 
NATURE 
It may be based on actions chemically or. 

[JUNE 10, 1915 

cell is highly sensitive towards ionic concentration. 
Confirming and extending the results obtained by 
Loeb in 1898, and using similar methods, Moore, 
Roaf, and Whitley have found by direct observations on 
the embryonic cells of Echinus that even small increase 
in the concentration of the negative ion (HO) will 
accelerate growth.'* But if the allxalinity be increased 
yet a little, pathological mitoses make their appear- 
ance, and at a slightly greater alkalinity the chemical 
actions necessary for the life and metabolism of the 
cell are inhibited. On the other hand, an increased 
aa 
concentration of the positive ion (H) from the first 
retards, and, if pushed further, inhibits, growth. The 
parallel with the action of alkaline sensitisers and acid 
retarders upon the film is obvious. 
Observations showing an abnormal lowering of 
acidity in the digestive secretions of cancerous patients 
have been made by several investigators. Messrs. 
Moore, Roaf, and Whitley in 1905 found that the 
diminution of hydrochloric acid in the stomach was 
independent of the location of the disease.** Copeman 
and Hake, in 1908, published results which failed to 
confirm those of Moore.‘* The question as regards 
the secretion of HCl cannot be regarded as finally 
settled. But a lowering of acidity as a frequent 
feature in cases of malignant disease seems to be 
accepted as proved. With old age a similar pheno- 
menon is observed, and with advancing years the 
liability to cancer increases. 
These facts suggest that the antagonistic action of 
the acid and the alkali in the cell is parallel with the 
antagonistic action of restrainer and sensitiser upon 
the film. The latter may be illustrated by a simple 
experiment on the film. A latent image is formed on 
a dry plate, either by brief exposure to light or by 
application of a sensitiser. The application of a wash 
of very dilute HCI left on the plate for a couple of 
minutes will then obliterate the latent image, as will 
be found upon applying a developer. The effect is 
best obtained with highly dilute acid. Such a strength 
as is said to prevail normally in the secretion of the 
stomach—o-2 to 0-4 per cent.—works effectively. 
The possibility that substances which act as sensi- 
tisers or restrainers on the film may act to promote 
or retard mitosis in the cell must be admitted from 
these results, some of which are obtained by direct 
experiment on the living cell. 
The fact that cancer of tongue, lip, and throat, 
and generally of parts around the mouth, is chiefly 
confined to the male sex has before now been regarded 
as raising a suspicion as to the injurious effects of 
tobacco smoking.15 
The effects of a solution of the volatile substances 
evolved from burnt tobacco, upon the film, support 
this inference. If tobacco smoke is bubbled through 
water, and a little of this water is poured on the photo- 
graphic plate in the dark, and again washed off, a 
vigorous latent image will be obtained, as develop- 
ment will demonstrate. 
Now C. and R. Hertwig and Galleotti1® mention 
nicotine as one of a few substances which they found, 
by direct observation on animal cells, produced patho- 
logical mitosis and derangement of cell-division closely 
similar to those which are observed in cancer growth. 
It is evident that we may find, in this indica- 
12 Moore, Roaf, and Whitley, Proc. Roy. Soc., Ser. B, vol. Ixxvii., October 
1905. 
18 Moore, Roaf, and Whitley, Proc. Roy. Soc., Ser. B, vol. Ixxvii., May, 
1905. 
ay Copeman and Hake, Proc. Roy, Soc.. Ser. B, vol. Ixxx., June, 1908. 
15 Statistics of cases treated in the Middlesex Hospital in 1913 show that 
the number of c-ses of the kind in the male and female sexes stand as 8.3 : 1. 
Archives, xxviii. p. 2. 
16 Referred to by Moore,’ Roaf, and Whitley, Proc. Roy. Soc., Ser. B, vol. 
xxvil., October, 1905. ‘ 

