Fig. 5.1 illustrates the anatomical structure of the human eye in horizontal section, identifying key components.

Problem Analysis:

The task involves identifying and labeling parts of the human eye based on two diagrams:
1. Fig. 5.1: A horizontal section of the human eye, showing labeled parts (V, W, X, Y, Z).
2. Fig. 5.2: A frontal view of the human eye, where some parts are already labeled (e.g., Z).

#### Part (a):
We need to identify the parts labeled V and W in Fig. 5.1.

#### Part (b):
We need to label the parts corresponding to X, Y, and Z in Fig. 5.2, using the information from Fig. 5.1. The part Z is already labeled in Fig. 5.2 as a reference.

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Solution:

#### Step 1: Identify Parts in Fig. 5.1
From the structure of the human eye in Fig. 5.1:
- V: This part is located at the front of the eye and appears to be the transparent, dome-shaped structure that covers the iris and pupil. This is the cornea.
- W: This part is located behind the cornea and appears to be a fluid-filled chamber. This is the vitreous humor.

Thus:
- V: Cornea
- W: Vitreous humor

#### Step 2: Match Parts in Fig. 5.2
Now, we need to match the parts labeled X, Y, and Z in Fig. 5.1 with their corresponding structures in Fig. 5.2.

- Z: In Fig. 5.1, Z is the colored ring surrounding the black circular area (the pupil). This is the iris. In Fig. 5.2, Z is already labeled as the iris, which confirms our identification.
- Y: In Fig. 5.1, Y is the black circular area in the center of the iris. This is the pupil.
- X: In Fig. 5.1, X is the structure located behind the iris and pupil. This is the lens.

Thus, the labels for Fig. 5.2 are:
- X: Lens
- Y: Pupil
- Z: Iris (already labeled)

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Final Answers:

#### Part (a):
- V: Cornea
- W: Vitreous humor

#### Part (b):
- X: Lens
- Y: Pupil
- Z: Iris

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Boxed Final Answer:

\[
\boxed{
\text{Part (a): V = Cornea, W = Vitreous humor}
}
\]
\[
\boxed{
\text{Part (b): X = Lens, Y = Pupil, Z = Iris}
}
\]