12.Practice.Tests.for.the.SAT_2015-2016_1128p

Section 81
Practice Test Nine
799
Directions: The passages below are followed by questions based on their content; questions following a pair of related
passages may also be based on the relationship between the paired passages. Answer the questions on the basis of
what is stated or implied in the passages and in any introductory material that may be provided.
Questions 7-19 are based on the following passages.
Passage 1
Surgeons can perform phenomenal feats. They
replace clogged coronary arteries with blood vessels
from the leg. They reconnect capillaries, tendons,
Line and nerves to reattach severed fingers. They even
( 5) refashion parts of intestines to create new bladders.
But surgeons find it difficult to reconstruct complicated
bones like the jawbone or those of the
inner ear. And only rarely can they replace large
bones lost to disease or injury.
(10) The challenge stems from the nature of bones.
Unlike other types of tissue, bones with one normal
shape cannot be reworked into other shapes.
Nor can doctors move large bones from one part
of the body to another without severely disabling
(15) a person. Existing treatments for bone defects are
all short-term and limited. Surgeons can replace
some diseased joints with plastic or metal implants,
but artificial hips or knees steadily loosen and
must be reconstructed every few years.
(20) Fortunately, surgeons are beginning to overcome
these obstacles by creating bone substitutes
from, of all things, muscle. The idea of making
bones from muscle is not all that strange. Muscle,
bone, fat, blood vessels, and bone marrow all
(25) develop in human embryos from the same loosely
organized tissue.
In 1987 scientists isolated a bone-inducing
protein called osteogenin from cows. Osteogenin
can make undifferentiated human tissue produce
(30) cartilage and bone. But few surgeons have used
osteogenin because it is hard to control. If sprinkled
directly onto a defect, for instance, the entire
area might stiffen to bone if a tiny bit fell on surrounding
blood vessels and nerves.
(35) More recently, plastic surgeons have circumvented
that snag by prefabricating bones away from the
immediate site of a defect. Flaps of animal thigh
muscles are taken and placed in osteogenin-coated
silicone-rubber molds of the desired shape.
(40) The molds are implanted in the same animal's abdomen
to provide a suitable biologic environment for
transforming muscle into bone. Within weeks, the
molds yield tiny, perfectly detailed bone segments.
So far, surgeons have made bones from muscles
( 45) in small animals but have not yet tried the process
in humans. For one thing, osteogenin is available
only in small amounts. Secondly, the safety and
effectiveness of the process must first be tested on
larger animals.
Passage 2
(50) We have entered a new era in medicine. In
scarcely more than a generation, artificial organs
have evolved from temporary substitutes to longfunctioning
devices. Millions of people live with
cardiac pacemakers, arterial grafts, hip-joint pros-
(55) theses, middle-ear implants, and intraocular lenses.
Eventually, artificial organs will allow ordinary,
healthy people to live longer-or, more appropriately,
to die young at a ripe age. So far, though,
even the best substitutes lag far behind their natural
(60) counterparts. But the obstacles to better implants
are not purely technical. Because such devices
require human testing, their development poses a
challenge to our cultural and ethical values.
Although many patients volunteer for tests of
(65) unproven medical devices, such altruism-and
the medical progress it engenders-is hampered
by medical ethicists and others who call for more
restrictions on human testing. While people favoring
restrictions are well-intentioned, their standards
(70) are inappropriate.
The only way to gain the information needed
for refining artificial organs is through experiments
on people. Research using animals will not
suffice. The mechanics of bone joints, for example,
(75) differ markedly from species to species. The
replacement of wrists, knees, and finger joints
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