6 
Williams, Fisher, and Udall: The Spavin Group. 17 
abundant serous exudate (serous arthritis) ; bluish-red discolor- 
ations of the serous membrane are observed. As the disease ad- 
vances one finds connective tissue proliferations and osseous 
degeneration of the ligament (arthritis deformans). In many 
cases these degenerative proliferations become constricted at 
their points of attachment to the capsular ligament and drop 
into the articular cavity where they are found as free joint bodies 
(Case No. V, femoro-tibial articulation). 
It will be seen that this disease has many lesions in common 
with arthritis deformans as described by Fréhner: “In human 
surgery deforming inflammation of the joints is a chronic, 
aseptic, senile arthritis (malum senale) which leads to severe 
and permanent changes in the entire joint. It is not character- 
ized by suppuration; it may have a spontaneous or traumatic 
origin; is either mono- or polyarticular; its favorite seat is in 
the joints of the knee, hip, shoulder, and elbow, on the fingers, 
and in the vertebral column. It is a non-febrile arthritis that is 
ushered in with stiffness, crackling, and slight pain in the in- 
volved joint; usually continuing during the life of the indi- 
vidual, and finally leads to deformity of the entire joint. 
Anatomically it consists of degeneration and new formation 
processes of the cartilage, bone, and joint capsule. 
““(a) In the articular cartilage one finds changes character- 
istic of arthritis ulcerosa-sicca chronica; namely, fibrillation of 
the superficial layers, focus-like areas of fibrillation and soften- 
ing of the deeper layers, ulceration, and even complete atrophy 
of the cartilage with the formation of smooth, polished surfacés. 
One also finds active proliferation of the cartilage in the form of 
nodular processes. 
“(b) In the bone there exists a subchondral inflammatory 
osteo-porosis with atrophy of the lacune in addition to bony new 
formation. 
““(¢) The joint capsule shows proliferation, thickening, and 
wrinkling. One occasionally observes the formation of free joint 
bodies.” (Bayer-Fréhner “ Tierarztliche Chirurgie und Geburts- 
hilfe Allgemeine Chirurgie,” 1905.) — 
While this group of diseases, of which spavin is a type, bears 
a very close resemblance to arthritis chronica deformans, there 
are certain features that are not characteristic of the latter affec- 
tion; namely, in the spavin group the changes in the first stages 
of the disease are confined largely to the bone (Fig. XII). In 
