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The Croonian Lecture. On the Changes the Blood undergoes in the 

 act of Coagulation. By SzrEverard Home, Bart. V.P.R.S. Read 

 November 20, 1817. [Phil. Trans. 1818,;?. 172.] 



After paying a tribute of applause to the talents of Mr. Bauer, as 

 a microscopical observer, the author proceeds to estimate the size of 

 the globules in human blood, 16 of which, when enveloped in their 

 colouring matter, occupy the space of the 160,000th part of a 

 square inch, so that 2,560,000 would be required to cover the super- 

 ficial inch ; but when the colouring matter is removed, 25 occupy 

 the 160,000th part of an inch, which gives 4,000,000 to the square 

 inch. The readiness with which the colouring matter is removed 

 by the action of water, and its large relative quantity compared to 

 the globule (being as about 3 to 1), induce the author to believe 

 that the colouring substance is distinct from and not contained in 

 the globules, but that it merely envelops them. The globules of 

 the blood are not of the same appearance in all animals : in the 

 skate they are of an oval form, and about twice as large as those in 

 human blood, and quite independent of the colouring matter. 



When the globules in the human blood have discharged their co- 

 lour, they coalesce by mutual attraction into various forms, repre- 

 sented in a drawing annexed to the paper. In one instance four 

 globules united so as to form a line with lateral indentations. The 

 author, struck with the analogy between this appearance and that 

 of a single muscular fibre, was induced to request Mr. Bauer to en- 

 deavour to unravel a muscle, so as, if possible, to compare its ulti- 

 mate fibre with the chain of adhering globules. In this attempt he 

 succeeded ; and the appearances under the microscope, which were 

 analogous, were given in an annexed drawing. It was further found 

 that by macerating muscular fibre it might be broken down into 

 colourless globules of the same size and appearance as those of the 

 blood. 



Having adduced these and other proofs and observations in favour 

 of the ultimate muscular fibre being formed of the colourless globu- 

 lar particles of the blood, and having noticed the globular structure 

 of the fibres of the brain, the author proceeds to consider in what 

 manner the blood, in the act of coagulation, acquires the tubular 

 texture, which fits it, when extravasated in living animals, to open a 

 communication with the circulation, and afterwards to become a part 

 of the solids of the animal. 



Guided by some curious observations of Mr. Bauer on the for- 

 mation of the tubular structure of plants, Sir Everard was induced 

 to believe that the extrication of air, during the coagulation of the 

 blood, might have an important influence upon its subsequent tex- 

 ture, and therefore observed what happened during the coagulation 

 of a drop of blood in the field of the microscope. At first a film of 

 coagulum formed upon the surface, air was then disengaged, which 

 passed in every direction through the serum, without interfering 

 with the globules, and formed a beautiful net-work of anastomosing 



