1538 
Bilharzia haematobium is terminal-spined, and the 
cercariz are found in the fresh-water molluscs, Bul- 
linus contortus and B, dybowskt, The egg of Bil- 
harzia mansoni is lateral-spined, and the cercariz 
occur in Planorbis boissyi, From these molluscs the 
cercariz escape, and were proved to enter experi- 
mental animals through the skin as well as through 
the mucous membrane of the mouth, 
Protozoa and Disease, 
Dr, Helen Pixell-Goodrich gave an account of the 
amoebe parasitic in man, namely, Entamoeba his- 
tolytica, the specific cause of amoebic dysentery, from 
the large intestine; E. gingivalis, from the mouth; and 
E. coli, a harmless species, feeding on the contents of 
its host’s intestine. Dr. Pixeil-Goodrich devoted 
special attention to FE. gingivalis in relation to 
pyorrhcea, but although this amoeba occurs so com- 
monly in these lesions, it was not considered to be 
the cause of the disease. The morphological similarity 
of the trophozoites of E. gingivalis and E. histolytica 
was pointed out, and the large characteristic inclusions 
of the former were held to be the nuclei of lympho- 
cytes. 
Dr. T. Goodey’s paper dealt with the results of ob- 
servations by Mr. Wellings and himself on E, gingi- 
valis, which they found in the mouths of both young 
and old persons wherever there was accumulation of 
food débris. They concluded that there is nothing to 
show that the organism is in any way causally con- 
nected with pyorrhcea, the food bodies being nuclear 
fragments of decomposed salivary corpuscles. 5 
Dr. Annie Porter gave an account of observations 
by’ Dr. H. B. Fantham and herself on the flagellate 
protozoa associated with dysentery, with special refer- 
ence to cases from Gallipoli. Trichomonas hominis 
has been found in cases of severe diarrhoea at Salo- 
nica; prophylaxis is directed to the prevention of con- 
tamination of food or water by infected material and 
by possible insect carriers and rodents (similar Tricho- 
monads occur in rats, mice, and rabbits), and to the 
isolation of human ‘‘carriers.’”’ Cases of Tetramitus 
diarrhoea have been found among patients from Egypt, 
Gallipoli, and Salonica. Giardia (Lamblia) intes- 
tinalis was found to be the commonest flagellate in 
the stools (3800) of the soldiers examined, and in some 
cases occurred in enormous numbers; one stool was 
estimated to contain 14,400,000,000. Giardia derived 
from man is pathogenic to kittens and mice, producing 
erosion of the intestinal cells. Rats, mice, and cats 
can act as “reservoirs,” and by contaminating the 
food and ‘drink of man may spread the organism. 
War and Eugenics. 
Mr, Hugh Richardson stated the case ‘for the insti- 
tution of an inquiry into the after-effects of war on 
population. He pointed out the nature of the evidence 
available or to be sought, the statistical methods to 
be employed, and, after referring to the various and 
dubious theories held in the past, indicated some of 
the problems which seemed capable of solution. Sub- 
sequent speakers—Dr. Chalmers Mitchell, Dr. Don- 
caster, Dr. Tocher, and Prof. MacBride—were em- 
phatic in supporting the case for an impartial inquiry 
and for the collection and preservation of statistical 
information by the Registrar-General, the Army re- 
cruiting staff, school medical services, and other 
sagencies. 
Dr. F, A, Dixey exhibited and commented upon a 
series of insects collected on the way to and from 
and in Australia in 1914. Mr. Heron-Allen exhibited 
lantern-slides illustrating the mussel fishery and the 
life of Alcide d’Orbigny at Esnandes. , 
NO. 2452, VOL. 98] 
NATURE 
[OcTOBER 26, 1916 
The Friday afternoon was devoted to a visit to the 
Dove Marine Laboratory at Cullercoats, the members 
being taken over the laboratory and aquarium by the 
director, Prof, Meek. J. H. AsHwortn, 
ENGINEERING AT THE BRITISH 
ASSOCIATION. 
M®: GERALD STONEY devoted his presidential 
address to a review of some of the errors com- 
mitted in the past by masters and men in the engineer- 
ing industry.. An abridgment of the address appears 
elsewhere in this issue of NaTuRE, 
After the address a paper on ** Limit Gauges ’ was 
read by Dr. R. T. Glazebrook, director of the National 
Physical Laboratory. 
its importance in the manufacture of munitions. The 
greatly increased scale of manufacture necessitated 
the production of an enormous number of gauges, both 
for workshop use and for testing. The National 
Physical Laboratory has acted as the checking autho- 
rity for the correctness of the gauges employed by the 
Government inspectors. Dr. Glazebrook first described 
the principles of limit gauging and then the various 
methods and apparatus evolved for dealing with the 
problem at the National Physical Laboratory. 
A paper on “ The Principle of Similitude in Engineer- 
ing Design’’ was read by Dr. T. E, Stanton, who 
discussed the possibilities and difficulties of obtaining 
accurate information for the design of structures, ships, 
aeroplanes, propellers, etc., from tests made on small 
models, 
The late Mr, Leslie Robertson, who was lost on the 
Hampshire, had promised to read a paper on the work — 
of the International Standards Committee. Mr. le 
Maistre, who has succeeded him as secretary of the 
committee, took over the task, and read an interesting 
paper on “Standardisation and its Influence on the 
Engineering Industries.” 
Mr. H. T. Newbigin described the raison d’étre of 
the Michell type of bearing. Already in common use 
for thrust bearings, it is now being experimentally 
applied to journal bearings. : 
Prof. W. M, Thornton discussed ‘‘The Influence of 
Pressure on the Electrical Ignition of Methane,” and 
described experiments showing that, as the pressure 
is gradually increased, the energy in the spark neces- 
sary to cause ignition increases in a stepped, discon- 
tinuous manner. 
Prof, W. H, Watkinson described some tests show- 
ing that Diesel engines could be worked satisfactorily 
with compression pressures considerably lower than — 
those usually employed. 
Prof. G. W. O. Howe read a paper on ‘‘ The Cal- 
culation of the Capacity of Aerials, including the 
Effects of Masts and Buildings.’’ Papers on this sub- 
ject were read by the author at the Sydney and Man- 
chester meetings; in the present paper the subject 
is carried further, and a number of numerical examples 
and experimental results are given which fully confirm 
the method of calculation, : 
Mr. McLachlan described the results of some experi- 
ments on a Poulsen arc, to determine the best mag- 
netic field strength to employ for maximum output 
and for maximum efficiency. 
The only research committee that reported at length 
was that on ‘‘Complex Stress Distribution,’ in con- 
nection with which Dr. Stanton exhibited a model of 
anew machine in use at the National Physical Labora- 
tory for subjecting a specimen to a rapidly reversing 
combination of bending and twisting. ; 
The last day of the meeting was devoted to a joint 
discussion with the Chemical Section of the report of 
the Committee on Fuel Economy. 
This subject has been forced 
upon the attention of the whole engineering world by 
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