620 
DEPARTMENT OF SURGERY. 
embedded in the other ( monstrosity ). This condition of 
things, though not very common, may be the cause of much 
trouble in delivering the foetus, especially when the foetus is 
large or the presentation faulty ; and, if the conformation of 
the mother is such that parturition is impossible, it is advisable 
to remove it by surgical means. 
4. Monstrosities. —The term monstrosity is generally ap¬ 
plied to a foetus that presents some defect in its conformation ; 
the condition may be organic, anomalous or pathological, and 
may involve a part of or the entire organism of the foetus. The 
subject of monstrosities to teratology, which is the part of morpho¬ 
logy that treats of the deviation in the development of embryos, 
has been well studied and thoroughly presented by Gurlt,j 
a noted German veterinarian, and Geoffroy Saint-Hilaire, an 
eminent French zoologist and comparative anatomist. Both of 
these authors have given to the profession a complete classifica¬ 
tion of these abnormalities, which can be used to a good advan¬ 
tage in the study of obstetrics ; but, for our purpose we shall 
divide them into but two classes, viz. : 
(a) Single monstrosities caused by excessive growth. 
(b) Monstrosities resulting from the union of foetuses. 
(a) Single Monstrosities caused by Excessive Growth of the 
foetus may extend through the entire body ( macrosomia ), and 
have a well developed symmetrical body, or may consist of an 
excessive development of any region, such as an abnormal de¬ 
velopment of the head (: megalocephalus ) ; however, one abnor¬ 
mality is usually accompanied by another or even more : e.g. 
an abnormal development of the head with an abnormal heart; 
or, the non-development of some portion of the body with the 
abnormal development of an organ. This condition (macrosis), 
of the foetus, whether local or general, is frequently the cause 
of dystokia, and when complicated by some maternal abnor¬ 
mality or deformity, may make delivery of the foetus impos¬ 
sible. 
(b) Monstrosities resulting from the Union of Foetuses .— 
The most common monstrosities of this class are those with 
two heads fephalodidymus ) (Fig. 28) ; and those with a 
double posterior extremity and but one head ( dipygus ) ; 
another very common example of these consists of a single head 
with a double trunk and posterior extremity ( cormo-melodidy- 
mus) ; besides these double monstrosities, there are a number of 
triple ( trigeminal ) that are occasionally found in domestic ani¬ 
mals ; the most common of these triple unions are those with 
