358 OF THE CIRCULATION OF THE BLOOD. 



was made in the skull, these vessels were then as completely emptied as the 

 rest. In the experiments performed by Kiissmaul and Tenner, 1 it was found 

 on trephining the skull and compressing the carotids, that the brain, especi- 

 ally after removal of the dura mater, became very pale, and retreated from 

 the opening to so great an extent as to form a cup 2} mm. in depth ; whilst 

 on releasing the pressure, it assumed a deep rose color and became convex. 

 When, however, they luted a piece of glass air-tight into the hole made by 

 the trephine, as suggested by Bonders, the phenomena were no longer the 

 same, for no movement of any kind could then be perceived in the brain, 

 which remained in all cases immovably in contact with the glass plate; but 

 the same changes in the tint of the cerebral substance, on checking and 

 again restoring the current in the arteries, were observed. Observations of 

 a similar nature were made by Mr. Durham 2 and Dr. Hammond, 3 by whom 

 it was noticed that the condition of the brain varied to a remarkable degree 

 in the sleeping and in the waking stales, being paler and ausemic in the 

 former, and comparatively congested in the latter. These experiments, 

 therefore, appear to furnish indisputable evidence that the circulation of 

 blood through the Brain varies with the general conditions of the vascular 

 system, and is not, as Dr. Kellie's experiments appeared to show, indepen- 

 dent of them. In M. Jolly's experiments a manometer luted into the skull of 

 dogs showed a positive pressure, which, rising with expiration and falling 

 with inspiration, was sufficient in general to support a column of water vary- 

 ing from one to six inches in height. In rabbits it was about half this amount, 

 and occasionally became negative. The pulse in dogs caused a variation of 

 from 5 to 10 mm. Compression of the carotids produced but little effect, but 

 the pressure slowly rose when the jugular veins were compressed. 4 Moreover, 

 in disordered states of the circulation, the quantity of blood in the vessels of 

 the cranium may be for a time diminished by a sudden extravasation, either 

 of blood or serum, into the cerebral substance; and the amount of interior 

 pressure upon the walls of the vessels may also be considerably altered, even 

 when there is no difference in the quantity of fluid contained in them. It 

 seems highly probable that in the delicate and extensive system of capilla- 

 ries found in the pia mater and choroid plexus, a provision is made by which 

 a large quantity of cerebrospinal fluid can be effused or absorbed in a short 

 space of time, to compensate for sudden changes in the balance of the cir- 

 culation. 



278. The Erectile Tissues present another curious modification of the ordi- 

 nary vascular apparatus. The chief of these are th corpora cavernosa in 

 the penis of the male, and in the clitoris of the female; the collection of 

 similar tissues round the vagina and in the nymplue and uterus (Rouget) 

 of the female; and the nipple in both sexes. In all these situations, erec- 



1 See their Essay (Syd Soc. Translation), p. 30 et seq., 1859. 

 -' Guy's Hosp. Rep., 1860, p. 149. 



3 New York Mod. Juurn., 1865, quoted in the Phv-ioln^v of Man, by Dr. Austin 

 Flint. 



4 See F. Jolly, Unter.swhnngen iiber den Gehirndniek und iiber dieBlutbewegung 

 ini Seh-idel, Wurzburg, 1871; see also G. Althaun, licit rnire. zur IMiy.-iolo^ie und 

 Pathologic <]cr Circulation, 1871. Pa^enstccher, Kxporimcnts und Studien iiber 

 Geliii ndniek ; and Cappie, The Relation of the Cranial Contents to tlie Pre.-sure of 

 the Atmosphere, 1874. 



5 The rcMilts of the experiments of Dr. G. P>urro\vs (Medical Ga/.ettc, April and 

 May, ISC!) fully confirm the views stated above. Pa^di-trclicr has shown that from 

 'J.'.i to <;."> per cent, of the cubic capacity of an animal's skull may he occupied by in- 

 jection of wax and tallow through a trephine aperture before symptoms of pressure 

 supervene. In other words, that taking the capacity of the >kull to he 1:!00-1400 

 c.e., from 37. 7-40. G c.e. as a mean, or 84.5-UO.O c.c. as maximum of blood may be, 

 effused without evidence of pressure. 



