a 5 oe Ms 
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NATURE 
267 
to the mechanical arrangement of its ultimate parts; (0) 
in regard to its chemical composition. 
The fourth and fifth lectures deal with, first, the varia- 
tions from the typical structure found in fibres taken from 
the same animal and grown at the same time, in fibres 
from the same animal grown in different years, in fibres 
from the same animal grown under different climatic and 
other conditions, and in fibres from different breeds of 
sheep grown in different countries; and, secondly, the 
effect of these variations in the manufacturing pro- 
cesses. 
There are a number of excellent illustrations which 
materially assist the reader. 
It has hitherto been too commonly supposed that the 
sheep might be turned out upon our bleak and barren 
hillsides, of which no other use could be made, and left 
to its own resources ; but this is doubtful economy, even 
as regards the land, and Dr. Bowman shows that as to 
the sheep it simply ruins the wool. “ The wool and its 
character depend very largely not only on the health of 
the sheep, but also upon climatic and other influences. 
The mildness or severity of the season and the plenty or 
scarcity of food very largely affect the character of the wool. 
In very severe seasons there is a tendency to a thicken- 
ing of the fibres, with greater irregularity in the length of 
the general staple and a greater rankness of the fleece, 
with undergrowth of short fibres and a greater irregularity 
in the diameters of the individual fibres and the different 
parts of the same fibre. The general character of the 
wool is also affected because from constant wetting and 
drying in the bad seasons the wool becomes tender and 
rotten. and loses its brilliancy and lustre.” “ When 
examined under the microscope the individual fibres are 
found to be injured in their structure by the want of 
proper nourishment and the deficiency in the natural suint 
or grease, a great part of which is soluble in water, and 
when removed leaves the fibres dry and hask. Of course 
amongst well tended flocks these variations are reduced 
to a minimum, because they are supplied with suitable 
shelters from the storms and fed artificially when there is 
a scarcity of pasture.” Most farmers think more of the 
mutton than of the wool, but whatever improves the one 
improves the other, and it would pay them well to devote 
more attention to the comforts of our hillside sheep, and 
even of ‘those which are pastured in more favourable 
situations. 
Great improvements have, we believe, been effected in 
apparatus for washing wool, but perhaps Dr. Bowman is 
right in saying that even yet sufficient attention is not 
paid to the temperature of the water. It seems to be for- 
gotten that wool is an animal matter and that “the real 
base of the wool fibre is a body which very closely re- 
sembles, and is allied to, the albumenoids, and all these 
bodies are subject to very great changes in molecular 
condition when subjected even to moderate degrees of 
heat.” Dr. Bowman made a number of experiments with 
“a bright-haired wool” to determine the effect on its 
lustre and strength of washing at different temperatures 
in pure water. He found that “ wool which looked quite 
bright when well washed with tepid water was decidedly 
duller when kept for some time in water at a temperature 
of 160° F. ; and the same wool, when subjected to boiling 
water 212° F., became quite dull and lustreless.” As Dr. 
Bowman elsewhere says, when water is heated by blowing 
in jets of steam, as is not unusual in wool-washing, the 
temperature varies in different parts, being nearly or 
quite 212° close to the steam jet, whilst very much lower 
at a little distance. W. H. S. W. 
PHYSIOLOGY OF THE EMBRYO 
Specielle Physiologie des Embryo. Untersuchungen tiber 
die Lebenserscheinungen vor der Geburt. Von W. 
Preyer. (Leipzig: Th. Grieben’s Verlag, 1885.) 
HE vital processes of the embryo present so many 
difficulties in their investigation that, in spite of 
their great interest, they have hitherto received only a 
small share of the physiologist’s attention. Prof. Preyer’s 
new book will therefore be received with welcome as an 
important contribution to our knowledge of the subject ; 
and is likely, on account of its completeness, to become a 
standard text-book. 
The work is an almost exhaustive summary (extending 
to more than 600 pp. 8vo) of the results of investigations 
into this branch of physiology from the time of Aristotle 
downwards. Indeed, so large a proportion of other men’s 
researches are included, that the title “ Untersuchungen 
. von W. Preyer” would seem to require modification. 
The reader may be a little disappointed with the earlier 
portion of the book, on account of the trite nature of some 
subjects which could hardly have been omitted ; but the 
matter increases in interest with the progress of the work, 
and especially where the author’s own researches are 
described. The style is not as condensed as could be 
wished: but this fault is not uncommon fin scientific 
writings. 
Although the common chick most rightly receives a 
large share of attention, yet other animals—mammalia, 
reptiles, and fishes—are not in any way neglected, and 
even invertebrates are occasionally touched upon. The 
most valuable observations are those on the guinea-pig, 
dog, &c. The author laments the scarcity of material 
and of opportunities for observation on the human sub- 
ject ; and recommends that in foundling hospitals and 
lying-in institutions a supply of apparatus should be kept 
ready for observing the physiology and pathology of the 
new-born ; since much may be learnt from the pheno- 
mena, especially the changes, which occur within the first 
minutes or hours after birth. 
In the first section, which treats of the embryonic cir- 
culation, Prof. Preyer shows the probability that in the 
chick the primitive blood, or haemolymph, begins to move 
before the occurrence of the first heart-beat. This he 
attributes to the effect of heat, the heart occupying a 
higher position in the embryo than the vessels, so that by 
convection the blood tends to rise towards the heart and 
distend it. This explanation is not satisfactory on physical 
grounds : for it is difficult to realise that there can be a 
difference of temperature between the contents of a minute 
vessel and its surroundings sufficient to cause such a 
movement. Is it not equally probable that the change of 
specific gravity may be due to chemical changes in the 
haemolymph ; cr, more probable than either, that the fluid 
is formed in the peripheral vessels and driven onwards 
by the pressure of osmosis ? 
