Marcu 3, 1904] 
SOCIETIES AND ACADEMIES. 
Lonpon. 
Royal Society, January 28.—‘‘ The * Islets of Langerhans’ 
of the Pancreas.’”?” By H. H. Dale, M.A., B.C., George 
Henry Lewes Student. Communicated by 'Prof. Starling, 
F.R.S. 
Since first described by Langerhans, in 1869, the “ islets "’ 
have had various functions assigned to them, on the assump- 
tion that they are independent structures embedded in the 
pancreatic tissue, the prevalent view regarding them as 
ductless glands furnishing an internal secretion necessary 
for normal carbohydrate metabolism. 
Lewaschew and others have stated that 
forms exist between the ‘‘islets’’ and the ordinary pan- 
creatic alveoli, and that the abundance of islets and the 
prevalence of intermediate forms are increased by activity 
of the gland. Lagnesse described a conversion of secretory 
alveoli into islets and vice versd during embryonic develop- 
ment. 
These observations were made on the pancreas of the 
dog, cat, rabbit and toad, in conditions of rest, exhaustion, 
starvation, and after ligature of the duct. The tissue was 
hardened in a sublimate-formaldehyde mixture, cut in 
paraffin, and stained with toluidine blue and eosine. 
In the resting pancreas of all the species examined, the 
intermediate forms described by Lewaschew were observed, 
and in the toad indications were found of a reconstruction 
of alveoli from islets. 
In the condition of 
intermediate 
exhaustion, produced, in the 
mammalian pancreas, by intravenous injection of secretin 
during anzsthesia, in that of the toad by hypodermic in- 
jection of the same substance, a very extensive conversion 
of secretory alveoli into ‘‘ islets’? was observed, specimens 
being obtained from a dog with the greater part of a lobule, 
from a toad with the greater part of the whole pancreas 
so converted. 
The effect of starvation, observed in a stray cat and in 
toads from the laboratory tank, was similar, but slighter 
in degree. 
In the dog and rabbit, occlusion of the duct caused an 
interstitial fibrosis, the areas of tissue not destroyed 
assuming the ‘‘islet’’ condition. The preformed islets 
appeared to have no special immunity. 
February 4.—‘ On the Origin of Parasitism in Fungi.’’ 
By George Massee (Principal Assistant, Herbarium, Royal 
Gardens, Kew). Communicated by Sir William T. 
Thiselton-Dyer, K.C.M.G., C.I.E., F.R.S. 
The hitherto unexplained problem as to why parasitic 
fungi are usually confined to one, or at most a few closely 
allied host-plants is shown to be due to chemotaxis. An 
extensive series of experiments was conducted with both 
parasitic and saprophytic fungi for the purpose of deter- 
mining the positive or negative chemotactic nature of 
various substances occurring normally in plants. Among 
such may be enumerated saccharose, glucose, asparagin, 
malic and oxalic acid, and pectase. Practically the germ 
tubes of all fungi are positively chemotactic to saccharose, 
and the reason why all plants containing this substance are 
not attacked by every kind of fungus is because certain 
other substances present in the plant are negatively chemo- 
tactic or repellent to the germ-tubes. 
Immune specimens of plants belonging to species attacked 
by an obligate parasite owe their immunity to the absence 
or small proportion of the substance chemotactic to the 
parasite. This discovery will assist in the production of 
immune strains of cultivated plants, all previous attempts 
in this direction having been conducted along lines of 
physical resistance. 
Purely saprophytic fungi can be educated to become para- 
sitic by sowing the spores on a living leaf that has had a 
substance positively chemotactic to the germ-tubes of the 
fungus experimented with injected into its tissues. By 
similar means a parasitic fungus can be led to attack a 
new host-plant. 
These experiments prove what has hitherto only been 
assumed, namely, that parasitism on the part of fungi is 
an acquired habit. 
Infection occurs more especially during the night or in 
dull damp weather, owing to the greater turgidity of the 
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WAT ORE 
429 
cells and to the presence in excess of the chemotactic sub- 
stance in the cell-sap. 
February 11.—‘ On Certain Properties of the Silver- 
Cadmium Series of Alloys.’’ By T. Kirke Rose, D.Sc. 
Communicated by C. T. Heycock, F.R.S. 
The attempts made at the Royal Mint to produce uni- 
form standard trial plates of silver and copper have been 
unsuccessful owing to the segregation of the constituents. 
The cooling curve of the alloy shows that solidification 
begins at goo° and ends at 778° after passing through a 
pasty stage, during which rearrangement of the con- 
stituents can take place, with the result that the uniform 
distribution of the silver is disturbed. The cooling curve 
of the alloy containing 92-5 per cent. of silver and 7-5 per 
cent. of cadmium is found to resemble that of a pure metal, 
showing no appreciable pasty stage, and on testing plates 
made of these materials they were found to be uniform in 
composition. The alloy is exceedingly ductile, and no 
difficulty is encountered in making assays on it ‘by any of 
the well-known methods. In preparing large ingots it is 
necessary to pour silver into a suitable amount of molten 
cadmium, this method minimising the loss of cadmium by 
volatilisation. The cooling curves and the microstructure 
of the whole series of alloys of silver and cadmium have 
also been studied, and evidence has been obtained of the 
existence of a number of compounds. The alloys contain- 
ing from 100 to 8o per cent. of silver are homogeneous at 
all temperatures below the solidus curve, although they 
appear to contain two bodies between the solidus and 
liquidus curves. 
“On the High Temperature Standards of the National 
Physical Laboratory: an Account of a Comparison of 
Platinum Thermometers and Thermo-junctions with the 
Gas Thermometer.’”’ By J. A. Harker, D.Sc. Com- 
municated by R. T. Glazebrook, F.R.S. 
This paper contains an account of a continuation of the 
work of Dr.’P. Chappuis and the author (Phil. Trans., A., 
1900) On a comparison of the scale of the gas thermometer 
with that of certain platinum thermometers, from below 
zero to 600° C. 
The results of this work confirmed the experiments of 
Callendar and Griffiths, and showed that the indications of 
the platinum thermometer may be reduced to the normal 
scale by the aid of Callendar’s difference formula 
d—=T—pt=8[(T/100)*—T/ too], 
where pt is the platinum temperature, T the temperature 
on the normal scale, and 6 a constant which, for pure 
platinum, is about 1-5. 
The temperatures chosen for the determination of 3 are 
o° C., 100° C., and the boiling point of sulphur. 
In the present paper the work is extended to a tempera- 
ture of 1000° C., a number of standard thermo-junctions 
of platinum—platinum-rhodium being also included in the 
comparisons. 
The gas thermometer employed for this work was pre- 
sented to the laboratory by Sir Andrew Noble. The bulbs 
used were of porcelain, glazed inside and out, and the gas 
used was pure dry nitrogen. The thermo-junctions were 
carefully compared at a number of fixed points up to 
g60° C., before use, with concordant results. A special 
potentiometer designed and made in the laboratory enabled 
the thermo-junction readings to be taken with great 
accuracy. 
The platinum thermometers employed were one of the 
three used by Harker and Chappuis in their earlier work, 
and a new one belonging to the British Association. The 
different instruments, after determination of their constants, 
were tested together in specially constructed electric resist- 
ance furnaces, heated from a special battery in which 
temperatures from 400°-1100° C. could be very steadily 
maintained for considerable periods. Special winding en- 
abled a compensation to be made for the greater cooling 
effect at the ends of the furnaces, so that over a consider- 
able length the temperature was exceedingly uniform. 
The investigation shows that :— 
(1) The readings of the platinum thermometers BA, and 
K,, which may be taken as representative instruments, 
when reduced to the air scale by the use of Callendar’s 
