44 
In a description of the sensitive laminae he speaks of an “elastic structure” occupy¬ 
ing the space between the laminae and the bone, as follows: 
“ This ” he says “ is a substratum of a fibrous periosteum like texture attaching 
the laminae to the coffin-bone, in which it is that the property of elasticity resides to 
that remarkable degree usually ascribed to the laminae themselves ; indeed so elastic is 
it found to be that it can be made to stretch like india rubber. Its fibres take a down¬ 
ward and backward direction. At the same time it affords a commodious bed for the 
ramifications of blood-vessels issuing from the substance of the bone, in which they are 
(particularly in the stretched condition of this substance) protected from injury, com¬ 
pression and consequent interruption to their circulation. 
“ The laminae ” he says “are not so highly organized as the sensitive sole, or frog 
for the obvious reason that all the blood they require is an amount necessary for their 
own nutrition and for the secretion of the horny laminae.” 
I shall not occupy any time to criticise any portion of this quotation. Percival like 
all contemporary writers held exaggerated notions concerning the elasticity of certain 
structures of the horse’s foot. His description of this what he calls an “elastic structure’’ 
includes the periosteum of the coffin-bone abundantly supplied both beneath the sensi¬ 
tive laminae and sensitive sole. 
It is the nutritive tissue, containing the secreting vessels which supply the compact 
tissue of the bone with food, and affording a protection to-the large vessels which pass 
into the interior of the bone for a similar purpose. 
It is a complex structure composed of an outer or fibrous portion and a germinal 
or nucleated membrane continued into the Haversian canals of the hard or compact 
tissue, supplying it and the lacunae with bone forming material. The outer portion 
forms the receptacle of the blood-vessels entering into the interior of the bone and the 
inner lining has a formative power of itself to reproduce bone from all subperiosteal 
exudates, as seen in the formation of splint ringbone and spavin. 
So far from its being considered and described as a tributary of the laminae, I 
should consider it the more important of the two, particularly in alluding to diseases 
of the feet, while the amount of work required of this tissue in maintaining a healthy 
condition of the parts underlying it, would appear to be very great, indicated by its 
abundant supply, as regards bulk and thickness. 
The effects of inflammation of this periosteal covering would be apparent, in al¬ 
teration of structure and form of the bone itself, and this is just what is found in almost 
every foot examined. 
The coffin-bone receives the larger part of its nutrition from the blood-vessels, sup¬ 
plied to its interior, passing beneath or through its periosteum and through the for- 
amean so plentifully seen on its outer surface. The branches of these nutrien- 
arteries anastomose with those supplied by the periosteum entering the haversian 
canals and lacunce. 
Inflammation of the periosteum affects the health of the bone by constricting the 
bloodvessels encompassed by it, these limiting the amount of blood passing through 
them. Inflammation of the cancellated structure of the bone supervening or occurring 
at the same time, causes a blocking up of the haversian canals and canaliculi constitu¬ 
ting what is known as the consolidative stage of inflammation of bone tissue, followed 
respectively by the rarefactive and ulcerative stages. 
It is a well known pathological fact that the blood-vessels of apart become atro¬ 
phied or decrease in adaptation to a part, until they contain no more blood, and 
furnish no more nutrition than is necessary to meet the diminished requirements of a 
